diff mbox series

[1/2] virtio-rng: implement entropy leak feature

Message ID 20230119184349.74072-2-bchalios@amazon.es (mailing list archive)
State Changes Requested
Delegated to: Herbert Xu
Headers show
Series virtio-rng entropy leak reporting feature | expand

Commit Message

Babis Chalios Jan. 19, 2023, 6:43 p.m. UTC
Implement the virtio-rng feature that allows a guest driver to request
from the device to perform certain operations in the event of an
"entropy leak", such as when taking a VM snapshot or restoring a VM from
a snapshot. The guest can request one of two operations: (i) fill a
buffer with random bytes, or (ii) perform a memory copy between two
bytes.

The feature is similar to Microsoft's Virtual Machine Generation ID and
it can be used to (1) avoid the race-condition that exists in our
current VMGENID implementation, between the time vcpus are resumed and
the ACPI notification is being handled and (2) provide mechanisms for
notifying user-space about snapshot-related events.

This commit implements the protocol between guest and device.
Additionally, it makes sure there is always a request for random bytes
in the event of entropy leak in-flight. Once such an event is observed,
the driver feeds these bytes to as entropy using
`add_device_randomness`.

Keep in mind that this commit does not solve the race-condition issue,
it adds fresh entropy whenever the driver handles the used buffer from
the fill-on-leak request. In order to close the race window, we need to
expose some API so that other kernel subsystems can request directly
notifications from the device.

Signed-off-by: Babis Chalios <bchalios@amazon.es>
---
 drivers/char/hw_random/virtio-rng.c | 200 +++++++++++++++++++++++++++-
 include/uapi/linux/virtio_rng.h     |   3 +
 2 files changed, 197 insertions(+), 6 deletions(-)

Comments

kernel test robot Jan. 19, 2023, 8:17 p.m. UTC | #1
Hi Babis,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus linus/master v6.2-rc4 next-20230119]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Babis-Chalios/virtio-rng-implement-entropy-leak-feature/20230120-024631
patch link:    https://lore.kernel.org/r/20230119184349.74072-2-bchalios%40amazon.es
patch subject: [PATCH 1/2] virtio-rng: implement entropy leak feature
config: parisc-allyesconfig (https://download.01.org/0day-ci/archive/20230120/202301200407.n4URhGEQ-lkp@intel.com/config)
compiler: hppa-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/686114cbba5005584d458ad44164b4a4b88135f5
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Babis-Chalios/virtio-rng-implement-entropy-leak-feature/20230120-024631
        git checkout 686114cbba5005584d458ad44164b4a4b88135f5
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=parisc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=parisc SHELL=/bin/bash drivers/char/hw_random/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   In file included from include/linux/err.h:8,
                    from drivers/char/hw_random/virtio-rng.c:8:
>> arch/parisc/include/uapi/asm/errno.h:7: warning: "ENOMSG" redefined
       7 | #define ENOMSG          35      /* No message of desired type */
         | 
   In file included from drivers/char/hw_random/virtio-rng.c:7:
   include/uapi/asm-generic/errno.h:23: note: this is the location of the previous definition
      23 | #define ENOMSG          42      /* No message of desired type */
         | 
>> arch/parisc/include/uapi/asm/errno.h:8: warning: "EIDRM" redefined
       8 | #define EIDRM           36      /* Identifier removed */
         | 
   include/uapi/asm-generic/errno.h:24: note: this is the location of the previous definition
      24 | #define EIDRM           43      /* Identifier removed */
         | 
>> arch/parisc/include/uapi/asm/errno.h:9: warning: "ECHRNG" redefined
       9 | #define ECHRNG          37      /* Channel number out of range */
         | 
   include/uapi/asm-generic/errno.h:25: note: this is the location of the previous definition
      25 | #define ECHRNG          44      /* Channel number out of range */
         | 
>> arch/parisc/include/uapi/asm/errno.h:10: warning: "EL2NSYNC" redefined
      10 | #define EL2NSYNC        38      /* Level 2 not synchronized */
         | 
   include/uapi/asm-generic/errno.h:26: note: this is the location of the previous definition
      26 | #define EL2NSYNC        45      /* Level 2 not synchronized */
         | 
>> arch/parisc/include/uapi/asm/errno.h:11: warning: "EL3HLT" redefined
      11 | #define EL3HLT          39      /* Level 3 halted */
         | 
   include/uapi/asm-generic/errno.h:27: note: this is the location of the previous definition
      27 | #define EL3HLT          46      /* Level 3 halted */
         | 
>> arch/parisc/include/uapi/asm/errno.h:12: warning: "EL3RST" redefined
      12 | #define EL3RST          40      /* Level 3 reset */
         | 
   include/uapi/asm-generic/errno.h:28: note: this is the location of the previous definition
      28 | #define EL3RST          47      /* Level 3 reset */
         | 
>> arch/parisc/include/uapi/asm/errno.h:13: warning: "ELNRNG" redefined
      13 | #define ELNRNG          41      /* Link number out of range */
         | 
   include/uapi/asm-generic/errno.h:29: note: this is the location of the previous definition
      29 | #define ELNRNG          48      /* Link number out of range */
         | 
>> arch/parisc/include/uapi/asm/errno.h:14: warning: "EUNATCH" redefined
      14 | #define EUNATCH         42      /* Protocol driver not attached */
         | 
   include/uapi/asm-generic/errno.h:30: note: this is the location of the previous definition
      30 | #define EUNATCH         49      /* Protocol driver not attached */
         | 
>> arch/parisc/include/uapi/asm/errno.h:15: warning: "ENOCSI" redefined
      15 | #define ENOCSI          43      /* No CSI structure available */
         | 
   include/uapi/asm-generic/errno.h:31: note: this is the location of the previous definition
      31 | #define ENOCSI          50      /* No CSI structure available */
         | 
>> arch/parisc/include/uapi/asm/errno.h:16: warning: "EL2HLT" redefined
      16 | #define EL2HLT          44      /* Level 2 halted */
         | 
   include/uapi/asm-generic/errno.h:32: note: this is the location of the previous definition
      32 | #define EL2HLT          51      /* Level 2 halted */
         | 
>> arch/parisc/include/uapi/asm/errno.h:17: warning: "EDEADLK" redefined
      17 | #define EDEADLK         45      /* Resource deadlock would occur */
         | 
   include/uapi/asm-generic/errno.h:7: note: this is the location of the previous definition
       7 | #define EDEADLK         35      /* Resource deadlock would occur */
         | 
>> arch/parisc/include/uapi/asm/errno.h:19: warning: "ENOLCK" redefined
      19 | #define ENOLCK          46      /* No record locks available */
         | 
   include/uapi/asm-generic/errno.h:9: note: this is the location of the previous definition
       9 | #define ENOLCK          37      /* No record locks available */
         | 
>> arch/parisc/include/uapi/asm/errno.h:20: warning: "EILSEQ" redefined
      20 | #define EILSEQ          47      /* Illegal byte sequence */
         | 
   include/uapi/asm-generic/errno.h:67: note: this is the location of the previous definition
      67 | #define EILSEQ          84      /* Illegal byte sequence */
         | 
>> arch/parisc/include/uapi/asm/errno.h:22: warning: "ENONET" redefined
      22 | #define ENONET          50      /* Machine is not on the network */
         | 
   include/uapi/asm-generic/errno.h:47: note: this is the location of the previous definition
      47 | #define ENONET          64      /* Machine is not on the network */
         | 
>> arch/parisc/include/uapi/asm/errno.h:23: warning: "ENODATA" redefined
      23 | #define ENODATA         51      /* No data available */
         | 
   include/uapi/asm-generic/errno.h:44: note: this is the location of the previous definition
      44 | #define ENODATA         61      /* No data available */
         | 
>> arch/parisc/include/uapi/asm/errno.h:24: warning: "ETIME" redefined
      24 | #define ETIME           52      /* Timer expired */
         | 
   include/uapi/asm-generic/errno.h:45: note: this is the location of the previous definition
      45 | #define ETIME           62      /* Timer expired */
         | 
>> arch/parisc/include/uapi/asm/errno.h:25: warning: "ENOSR" redefined
      25 | #define ENOSR           53      /* Out of streams resources */
         | 
   include/uapi/asm-generic/errno.h:46: note: this is the location of the previous definition
      46 | #define ENOSR           63      /* Out of streams resources */
         | 
>> arch/parisc/include/uapi/asm/errno.h:26: warning: "ENOSTR" redefined
      26 | #define ENOSTR          54      /* Device not a stream */
         | 
   include/uapi/asm-generic/errno.h:43: note: this is the location of the previous definition
      43 | #define ENOSTR          60      /* Device not a stream */
         | 
>> arch/parisc/include/uapi/asm/errno.h:27: warning: "ENOPKG" redefined
      27 | #define ENOPKG          55      /* Package not installed */
         | 
   include/uapi/asm-generic/errno.h:48: note: this is the location of the previous definition
      48 | #define ENOPKG          65      /* Package not installed */
         | 
>> arch/parisc/include/uapi/asm/errno.h:29: warning: "ENOLINK" redefined
      29 | #define ENOLINK         57      /* Link has been severed */
         | 
   include/uapi/asm-generic/errno.h:50: note: this is the location of the previous definition
      50 | #define ENOLINK         67      /* Link has been severed */
         | 
   arch/parisc/include/uapi/asm/errno.h:30: warning: "EADV" redefined
      30 | #define EADV            58      /* Advertise error */
         | 
   include/uapi/asm-generic/errno.h:51: note: this is the location of the previous definition
      51 | #define EADV            68      /* Advertise error */
         | 
   arch/parisc/include/uapi/asm/errno.h:31: warning: "ESRMNT" redefined
      31 | #define ESRMNT          59      /* Srmount error */
         | 
   include/uapi/asm-generic/errno.h:52: note: this is the location of the previous definition
      52 | #define ESRMNT          69      /* Srmount error */
         | 
   arch/parisc/include/uapi/asm/errno.h:32: warning: "ECOMM" redefined
      32 | #define ECOMM           60      /* Communication error on send */
         | 
   include/uapi/asm-generic/errno.h:53: note: this is the location of the previous definition
      53 | #define ECOMM           70      /* Communication error on send */
         | 
   arch/parisc/include/uapi/asm/errno.h:33: warning: "EPROTO" redefined
      33 | #define EPROTO          61      /* Protocol error */
         | 
   include/uapi/asm-generic/errno.h:54: note: this is the location of the previous definition
      54 | #define EPROTO          71      /* Protocol error */
         | 
   arch/parisc/include/uapi/asm/errno.h:35: warning: "EMULTIHOP" redefined
      35 | #define EMULTIHOP       64      /* Multihop attempted */
         | 
   include/uapi/asm-generic/errno.h:55: note: this is the location of the previous definition
      55 | #define EMULTIHOP       72      /* Multihop attempted */
         | 
   arch/parisc/include/uapi/asm/errno.h:37: warning: "EDOTDOT" redefined
      37 | #define EDOTDOT         66      /* RFS specific error */
         | 
   include/uapi/asm-generic/errno.h:56: note: this is the location of the previous definition
      56 | #define EDOTDOT         73      /* RFS specific error */
         | 
   arch/parisc/include/uapi/asm/errno.h:38: warning: "EBADMSG" redefined
      38 | #define EBADMSG         67      /* Not a data message */
         | 
   include/uapi/asm-generic/errno.h:57: note: this is the location of the previous definition
      57 | #define EBADMSG         74      /* Not a data message */
         | 
   arch/parisc/include/uapi/asm/errno.h:39: warning: "EUSERS" redefined
      39 | #define EUSERS          68      /* Too many users */
         | 
   include/uapi/asm-generic/errno.h:70: note: this is the location of the previous definition
      70 | #define EUSERS          87      /* Too many users */
         | 
   arch/parisc/include/uapi/asm/errno.h:40: warning: "EDQUOT" redefined
      40 | #define EDQUOT          69      /* Quota exceeded */
         | 
   include/uapi/asm-generic/errno.h:105: note: this is the location of the previous definition
     105 | #define EDQUOT          122     /* Quota exceeded */
         | 
   arch/parisc/include/uapi/asm/errno.h:41: warning: "ESTALE" redefined
      41 | #define ESTALE          70      /* Stale file handle */
         | 
   include/uapi/asm-generic/errno.h:99: note: this is the location of the previous definition
      99 | #define ESTALE          116     /* Stale file handle */
         | 
   arch/parisc/include/uapi/asm/errno.h:42: warning: "EREMOTE" redefined
      42 | #define EREMOTE         71      /* Object is remote */
         | 
   include/uapi/asm-generic/errno.h:49: note: this is the location of the previous definition
      49 | #define EREMOTE         66      /* Object is remote */
         | 
   arch/parisc/include/uapi/asm/errno.h:43: warning: "EOVERFLOW" redefined
      43 | #define EOVERFLOW       72      /* Value too large for defined data type */
         | 
   include/uapi/asm-generic/errno.h:58: note: this is the location of the previous definition
      58 | #define EOVERFLOW       75      /* Value too large for defined data type */
         | 
   arch/parisc/include/uapi/asm/errno.h:47: warning: "EBADE" redefined
      47 | #define EBADE           160     /* Invalid exchange */
         | 
   include/uapi/asm-generic/errno.h:33: note: this is the location of the previous definition
      33 | #define EBADE           52      /* Invalid exchange */
         | 
   arch/parisc/include/uapi/asm/errno.h:48: warning: "EBADR" redefined
      48 | #define EBADR           161     /* Invalid request descriptor */
         | 
   include/uapi/asm-generic/errno.h:34: note: this is the location of the previous definition
      34 | #define EBADR           53      /* Invalid request descriptor */
         | 
   arch/parisc/include/uapi/asm/errno.h:49: warning: "EXFULL" redefined
      49 | #define EXFULL          162     /* Exchange full */
         | 
   include/uapi/asm-generic/errno.h:35: note: this is the location of the previous definition
      35 | #define EXFULL          54      /* Exchange full */
         | 
   arch/parisc/include/uapi/asm/errno.h:50: warning: "ENOANO" redefined
      50 | #define ENOANO          163     /* No anode */
         | 
   include/uapi/asm-generic/errno.h:36: note: this is the location of the previous definition
      36 | #define ENOANO          55      /* No anode */


vim +/ENOMSG +7 arch/parisc/include/uapi/asm/errno.h

^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16    6  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   @7  #define	ENOMSG		35	/* No message of desired type */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   @8  #define	EIDRM		36	/* Identifier removed */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   @9  #define	ECHRNG		37	/* Channel number out of range */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @10  #define	EL2NSYNC	38	/* Level 2 not synchronized */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @11  #define	EL3HLT		39	/* Level 3 halted */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @12  #define	EL3RST		40	/* Level 3 reset */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @13  #define	ELNRNG		41	/* Link number out of range */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @14  #define	EUNATCH		42	/* Protocol driver not attached */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @15  #define	ENOCSI		43	/* No CSI structure available */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @16  #define	EL2HLT		44	/* Level 2 halted */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @17  #define	EDEADLK		45	/* Resource deadlock would occur */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   18  #define	EDEADLOCK	EDEADLK
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @19  #define	ENOLCK		46	/* No record locks available */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @20  #define	EILSEQ		47	/* Illegal byte sequence */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   21  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @22  #define	ENONET		50	/* Machine is not on the network */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @23  #define	ENODATA		51	/* No data available */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @24  #define	ETIME		52	/* Timer expired */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @25  #define	ENOSR		53	/* Out of streams resources */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @26  #define	ENOSTR		54	/* Device not a stream */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @27  #define	ENOPKG		55	/* Package not installed */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   28  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @29  #define	ENOLINK		57	/* Link has been severed */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @30  #define	EADV		58	/* Advertise error */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @31  #define	ESRMNT		59	/* Srmount error */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @32  #define	ECOMM		60	/* Communication error on send */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @33  #define	EPROTO		61	/* Protocol error */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   34  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @35  #define	EMULTIHOP	64	/* Multihop attempted */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   36  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @37  #define	EDOTDOT		66	/* RFS specific error */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @38  #define	EBADMSG		67	/* Not a data message */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @39  #define	EUSERS		68	/* Too many users */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @40  #define	EDQUOT		69	/* Quota exceeded */
0ca43435188b9f arch/parisc/include/uapi/asm/errno.h Eric Sandeen        2013-11-12  @41  #define	ESTALE		70	/* Stale file handle */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @42  #define	EREMOTE		71	/* Object is remote */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @43  #define	EOVERFLOW	72	/* Value too large for defined data type */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   44  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   45  /* these errnos are defined by Linux but not HPUX. */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   46  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @47  #define	EBADE		160	/* Invalid exchange */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @48  #define	EBADR		161	/* Invalid request descriptor */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @49  #define	EXFULL		162	/* Exchange full */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @50  #define	ENOANO		163	/* No anode */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @51  #define	EBADRQC		164	/* Invalid request code */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @52  #define	EBADSLT		165	/* Invalid slot */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @53  #define	EBFONT		166	/* Bad font file format */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @54  #define	ENOTUNIQ	167	/* Name not unique on network */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @55  #define	EBADFD		168	/* File descriptor in bad state */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @56  #define	EREMCHG		169	/* Remote address changed */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @57  #define	ELIBACC		170	/* Can not access a needed shared library */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @58  #define	ELIBBAD		171	/* Accessing a corrupted shared library */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @59  #define	ELIBSCN		172	/* .lib section in a.out corrupted */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @60  #define	ELIBMAX		173	/* Attempting to link in too many shared libraries */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @61  #define	ELIBEXEC	174	/* Cannot exec a shared library directly */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @62  #define	ERESTART	175	/* Interrupted system call should be restarted */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @63  #define	ESTRPIPE	176	/* Streams pipe error */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @64  #define	EUCLEAN		177	/* Structure needs cleaning */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @65  #define	ENOTNAM		178	/* Not a XENIX named type file */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @66  #define	ENAVAIL		179	/* No XENIX semaphores available */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @67  #define	EISNAM		180	/* Is a named type file */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @68  #define	EREMOTEIO	181	/* Remote I/O error */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @69  #define	ENOMEDIUM	182	/* No medium found */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @70  #define	EMEDIUMTYPE	183	/* Wrong medium type */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @71  #define	ENOKEY		184	/* Required key not available */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @72  #define	EKEYEXPIRED	185	/* Key has expired */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @73  #define	EKEYREVOKED	186	/* Key has been revoked */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @74  #define	EKEYREJECTED	187	/* Key was rejected by service */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   75  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   76  /* We now return you to your regularly scheduled HPUX. */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   77  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16   78  #define ENOSYM		215	/* symbol does not exist in executable */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @79  #define	ENOTSOCK	216	/* Socket operation on non-socket */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @80  #define	EDESTADDRREQ	217	/* Destination address required */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @81  #define	EMSGSIZE	218	/* Message too long */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @82  #define	EPROTOTYPE	219	/* Protocol wrong type for socket */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @83  #define	ENOPROTOOPT	220	/* Protocol not available */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @84  #define	EPROTONOSUPPORT	221	/* Protocol not supported */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @85  #define	ESOCKTNOSUPPORT	222	/* Socket type not supported */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @86  #define	EOPNOTSUPP	223	/* Operation not supported on transport endpoint */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @87  #define	EPFNOSUPPORT	224	/* Protocol family not supported */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @88  #define	EAFNOSUPPORT	225	/* Address family not supported by protocol */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @89  #define	EADDRINUSE	226	/* Address already in use */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @90  #define	EADDRNOTAVAIL	227	/* Cannot assign requested address */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @91  #define	ENETDOWN	228	/* Network is down */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @92  #define	ENETUNREACH	229	/* Network is unreachable */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @93  #define	ENETRESET	230	/* Network dropped connection because of reset */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @94  #define	ECONNABORTED	231	/* Software caused connection abort */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @95  #define	ECONNRESET	232	/* Connection reset by peer */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @96  #define	ENOBUFS		233	/* No buffer space available */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @97  #define	EISCONN		234	/* Transport endpoint is already connected */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @98  #define	ENOTCONN	235	/* Transport endpoint is not connected */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  @99  #define	ESHUTDOWN	236	/* Cannot send after transport endpoint shutdown */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @100  #define	ETOOMANYREFS	237	/* Too many references: cannot splice */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @101  #define	ETIMEDOUT	238	/* Connection timed out */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @102  #define	ECONNREFUSED	239	/* Connection refused */
3eb53b20d7bd13 arch/parisc/include/uapi/asm/errno.h Helge Deller        2016-08-20  103  #define	EREFUSED	ECONNREFUSED	/* for HP's NFS apparently */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  104  #define	EREMOTERELEASE	240	/* Remote peer released connection */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @105  #define	EHOSTDOWN	241	/* Host is down */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @106  #define	EHOSTUNREACH	242	/* No route to host */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  107  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @108  #define	EALREADY	244	/* Operation already in progress */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @109  #define	EINPROGRESS	245	/* Operation now in progress */
f5a408d53edef3 arch/parisc/include/uapi/asm/errno.h Guy Martin          2014-01-16  110  #define	EWOULDBLOCK	EAGAIN	/* Operation would block (Not HPUX compliant) */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @111  #define	ENOTEMPTY	247	/* Directory not empty */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @112  #define	ENAMETOOLONG	248	/* File name too long */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @113  #define	ELOOP		249	/* Too many symbolic links encountered */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16 @114  #define	ENOSYS		251	/* Function not implemented */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  115  
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  116  #define ECANCELLED	253	/* aio request was canceled before complete (POSIX.4 / HPUX) */
05aa10de701409 include/asm-parisc/errno.h           Grant Grundler      2005-10-21 @117  #define ECANCELED	ECANCELLED	/* SuSv3 and Solaris wants one 'L' */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  118  
4750e2c0c59e0c include/asm-parisc/errno.h           Joe Korty           2005-05-01  119  /* for robust mutexes */
4750e2c0c59e0c include/asm-parisc/errno.h           Joe Korty           2005-05-01 @120  #define EOWNERDEAD	254	/* Owner died */
4750e2c0c59e0c include/asm-parisc/errno.h           Joe Korty           2005-05-01 @121  #define ENOTRECOVERABLE	255	/* State not recoverable */
4750e2c0c59e0c include/asm-parisc/errno.h           Joe Korty           2005-05-01  122  
7d217d7ffc3433 arch/parisc/include/asm/errno.h      Alexander Beregalov 2009-06-07 @123  #define	ERFKILL		256	/* Operation not possible due to RF-kill */
^1da177e4c3f41 include/asm-parisc/errno.h           Linus Torvalds      2005-04-16  124  
69ebb83e13e514 arch/parisc/include/asm/errno.h      Huang Ying          2011-01-30 @125  #define EHWPOISON	257	/* Memory page has hardware error */
69ebb83e13e514 arch/parisc/include/asm/errno.h      Huang Ying          2011-01-30  126
kernel test robot Jan. 20, 2023, 1:24 a.m. UTC | #2
Hi Babis,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus linus/master v6.2-rc4 next-20230119]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Babis-Chalios/virtio-rng-implement-entropy-leak-feature/20230120-024631
patch link:    https://lore.kernel.org/r/20230119184349.74072-2-bchalios%40amazon.es
patch subject: [PATCH 1/2] virtio-rng: implement entropy leak feature
config: x86_64-randconfig-s021 (https://download.01.org/0day-ci/archive/20230120/202301200941.fE9QkyE3-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-39-gce1a6720-dirty
        # https://github.com/intel-lab-lkp/linux/commit/686114cbba5005584d458ad44164b4a4b88135f5
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Babis-Chalios/virtio-rng-implement-entropy-leak-feature/20230120-024631
        git checkout 686114cbba5005584d458ad44164b4a4b88135f5
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/char/hw_random/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

sparse warnings: (new ones prefixed by >>)
>> drivers/char/hw_random/virtio-rng.c:59:5: sparse: sparse: symbol 'add_fill_on_leak_request' was not declared. Should it be static?
>> drivers/char/hw_random/virtio-rng.c:73:5: sparse: sparse: symbol 'virtrng_fill_on_leak' was not declared. Should it be static?
>> drivers/char/hw_random/virtio-rng.c:94:5: sparse: sparse: symbol 'add_copy_on_leak_request' was not declared. Should it be static?
>> drivers/char/hw_random/virtio-rng.c:113:5: sparse: sparse: symbol 'virtrng_copy_on_leak' was not declared. Should it be static?
Michael S. Tsirkin Jan. 20, 2023, 12:32 p.m. UTC | #3
On Thu, Jan 19, 2023 at 07:43:47PM +0100, Babis Chalios wrote:
> Implement the virtio-rng feature that allows a guest driver to request
> from the device to perform certain operations in the event of an
> "entropy leak", such as when taking a VM snapshot or restoring a VM from
> a snapshot. The guest can request one of two operations: (i) fill a
> buffer with random bytes, or (ii) perform a memory copy between two
> bytes.
> 
> The feature is similar to Microsoft's Virtual Machine Generation ID and
> it can be used to (1) avoid the race-condition that exists in our
> current VMGENID implementation, between the time vcpus are resumed and
> the ACPI notification is being handled and (2) provide mechanisms for
> notifying user-space about snapshot-related events.
> 
> This commit implements the protocol between guest and device.
> Additionally, it makes sure there is always a request for random bytes
> in the event of entropy leak in-flight. Once such an event is observed,
> the driver feeds these bytes to as entropy using
> `add_device_randomness`.
> 
> Keep in mind that this commit does not solve the race-condition issue,
> it adds fresh entropy whenever the driver handles the used buffer from
> the fill-on-leak request. In order to close the race window, we need to
> expose some API so that other kernel subsystems can request directly
> notifications from the device.
> 
> Signed-off-by: Babis Chalios <bchalios@amazon.es>
> ---
>  drivers/char/hw_random/virtio-rng.c | 200 +++++++++++++++++++++++++++-
>  include/uapi/linux/virtio_rng.h     |   3 +
>  2 files changed, 197 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
> index a6f3a8a2aca6..389a091a8801 100644
> --- a/drivers/char/hw_random/virtio-rng.c
> +++ b/drivers/char/hw_random/virtio-rng.c
> @@ -4,12 +4,14 @@
>   *  Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
>   */
>  
> +#include "asm-generic/errno.h"

Why are you pulling this in?
If you really need errno the thing to include
is linux/errno.h

checkpatch has a rule to catch such cases:

# warn if <asm/foo.h> is #included and <linux/foo.h> is available and includes
# itself <asm/foo.h> (uses RAW line)    

did you run checkpatch?


>  #include <linux/err.h>
>  #include <linux/hw_random.h>
>  #include <linux/scatterlist.h>
>  #include <linux/spinlock.h>
>  #include <linux/virtio.h>
>  #include <linux/virtio_rng.h>
> +#include <linux/random.h>
>  #include <linux/module.h>
>  #include <linux/slab.h>
>  
> @@ -18,6 +20,12 @@ static DEFINE_IDA(rng_index_ida);
>  struct virtrng_info {
>  	struct hwrng hwrng;
>  	struct virtqueue *vq;
> +	/* Leak queues */
> +	bool has_leakqs;
> +	struct virtqueue *leakq[2];
> +	spinlock_t lock;
> +	int active_leakq;
> +
>  	char name[25];
>  	int index;
>  	bool hwrng_register_done;
> @@ -29,27 +37,159 @@ struct virtrng_info {
>  	/* minimal size returned by rng_buffer_size() */
>  #if SMP_CACHE_BYTES < 32
>  	u8 data[32];
> +	u8 leak_data[32];
>  #else
>  	u8 data[SMP_CACHE_BYTES];
> +	u8 leak_data[SMP_CACHE_BYTES];
>  #endif
>  };
>  
> +/* Swaps the queues and returns the new active leak queue. */
> +static struct virtqueue *swap_leakqs(struct virtrng_info *vi)
> +{
> +	vi->active_leakq = 1 - vi->active_leakq;
> +	return vi->leakq[vi->active_leakq];
> +}
> +
> +static struct virtqueue *get_active_leakq(struct virtrng_info *vi)
> +{
> +	return vi->leakq[vi->active_leakq];
> +}
> +
> +int add_fill_on_leak_request(struct virtrng_info *vi, struct virtqueue *vq, void *data, size_t len)
> +{
> +	struct scatterlist sg;
> +	int ret;
> +
> +	sg_init_one(&sg, data, len);
> +	ret = virtqueue_add_inbuf(vq, &sg, 1, data, GFP_KERNEL);
> +	if (ret)
> +		goto err;
> +
> +err:
> +	return ret;
> +}
> +
> +int virtrng_fill_on_leak(struct virtrng_info *vi, void *data, size_t len)
> +{
> +	struct virtqueue *vq;
> +	unsigned long flags;
> +	int ret;
> +
> +	if (!vi->has_leakqs)
> +		return -EOPNOTSUPP;
> +
> +	spin_lock_irqsave(&vi->lock, flags);
> +
> +	vq = get_active_leakq(vi);
> +	ret = add_fill_on_leak_request(vi, vq, data, len);
> +	if (ret)
> +		virtqueue_kick(vq);
> +
> +	spin_unlock_irqrestore(&vi->lock, flags);
> +
> +	return ret;
> +}
> +
> +int add_copy_on_leak_request(struct virtrng_info *vi, struct virtqueue *vq,
> +		void *to, void *from, size_t len)
> +{
> +	int ret;
> +	struct scatterlist out, in, *sgs[2];
> +
> +	sg_init_one(&out, from, len);
> +	sgs[0] = &out;
> +	sg_init_one(&in, to, len);
> +	sgs[1] = &in;
> +
> +	ret = virtqueue_add_sgs(vq, sgs, 1, 1, to, GFP_KERNEL);
> +	if (ret)
> +		goto err;
> +
> +err:
> +	return ret;
> +}
> +
> +int virtrng_copy_on_leak(struct virtrng_info *vi, void *to, void *from, size_t len)
> +{
> +	struct virtqueue *vq;
> +	unsigned long flags;
> +	int ret;
> +
> +	if (!vi->has_leakqs)
> +		return -EOPNOTSUPP;
> +
> +	spin_lock_irqsave(&vi->lock, flags);
> +
> +	vq = get_active_leakq(vi);
> +	ret = add_copy_on_leak_request(vi, vq, to, from, len);
> +	if (ret)
> +		virtqueue_kick(vq);
> +
> +	spin_unlock_irqrestore(&vi->lock, flags);
> +
> +	return ret;
> +}
> +
> +static void entropy_leak_detected(struct virtqueue *vq)
> +{
> +	struct virtrng_info *vi = vq->vdev->priv;
> +	struct virtqueue *activeq;
> +	unsigned int len;
> +	unsigned long flags;
> +	void *buffer;
> +	bool kick_activeq = false;
> +
> +	spin_lock_irqsave(&vi->lock, flags);
> +
> +	activeq = get_active_leakq(vi);
> +	/* Drain all the used buffers from the queue */
> +	while ((buffer = virtqueue_get_buf(vq, &len)) != NULL) {
> +		if (vq == activeq) {
> +			pr_debug("%s: entropy leak detected!", vi->name);
> +			activeq = swap_leakqs(vi);
> +		}
> +
> +		if (buffer == vi->leak_data) {
> +			add_device_randomness(vi->leak_data, sizeof(vi->leak_data));
> +
> +			/* Ensure we always have a pending request for random bytes on entropy
> +			 * leak. Do it here, after we have swapped leak queues, so it gets handled
> +			 * with the next entropy leak event.
> +			 */
> +			add_fill_on_leak_request(vi, activeq, vi->leak_data, sizeof(vi->leak_data));
> +			kick_activeq = true;
> +		}
> +	}
> +
> +	if (kick_activeq)
> +		virtqueue_kick(activeq);
> +
> +	spin_unlock_irqrestore(&vi->lock, flags);
> +}
> +
>  static void random_recv_done(struct virtqueue *vq)
>  {
>  	struct virtrng_info *vi = vq->vdev->priv;
> +	unsigned long flags;
>  
> +	spin_lock_irqsave(&vi->lock, flags);
>  	/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
>  	if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
> -		return;
> +		goto unlock;
>  
>  	vi->data_idx = 0;
>  
>  	complete(&vi->have_data);
> +
> +unlock:
> +	spin_unlock_irqrestore(&vi->lock, flags);
>  }
>  
>  static void request_entropy(struct virtrng_info *vi)
>  {
>  	struct scatterlist sg;
> +	unsigned long flags;
>  
>  	reinit_completion(&vi->have_data);
>  	vi->data_avail = 0;
> @@ -57,10 +197,12 @@ static void request_entropy(struct virtrng_info *vi)
>  
>  	sg_init_one(&sg, vi->data, sizeof(vi->data));
>  
> +	spin_lock_irqsave(&vi->lock, flags);
>  	/* There should always be room for one buffer. */
>  	virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL);
>  
>  	virtqueue_kick(vi->vq);
> +	spin_unlock_irqrestore(&vi->lock, flags);
>  }
>  
>  static unsigned int copy_data(struct virtrng_info *vi, void *buf,
> @@ -126,6 +268,40 @@ static void virtio_cleanup(struct hwrng *rng)
>  	complete(&vi->have_data);
>  }
>  
> +static int init_virtqueues(struct virtrng_info *vi, struct virtio_device *vdev)
> +{
> +	int ret = -ENOMEM, total_vqs = 1;
> +	struct virtqueue *vqs[3];
> +	const char *names[3];
> +	vq_callback_t *callbacks[3];
> +
> +	if (vi->has_leakqs)
> +		total_vqs = 3;
> +
> +	callbacks[0] = random_recv_done;
> +	names[0] = "input";
> +	if (vi->has_leakqs) {
> +		callbacks[1] = entropy_leak_detected;
> +		names[1] = "leakq.1";
> +		callbacks[2] = entropy_leak_detected;
> +		names[2] = "leakq.2";
> +	}
> +
> +	ret = virtio_find_vqs(vdev, total_vqs, vqs, callbacks, names, NULL);
> +	if (ret)
> +		goto err;
> +
> +	vi->vq = vqs[0];
> +
> +	if (vi->has_leakqs) {
> +		vi->leakq[0] = vqs[1];
> +		vi->leakq[1] = vqs[2];
> +	}
> +
> +err:
> +	return ret;
> +}
> +
>  static int probe_common(struct virtio_device *vdev)
>  {
>  	int err, index;
> @@ -152,18 +328,24 @@ static int probe_common(struct virtio_device *vdev)
>  	};
>  	vdev->priv = vi;
>  
> -	/* We expect a single virtqueue. */
> -	vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
> -	if (IS_ERR(vi->vq)) {
> -		err = PTR_ERR(vi->vq);
> -		goto err_find;
> +	vi->has_leakqs = virtio_has_feature(vdev, VIRTIO_RNG_F_LEAK);
> +	if (vi->has_leakqs) {
> +		spin_lock_init(&vi->lock);
> +		vi->active_leakq = 0;
>  	}
>  
> +	err = init_virtqueues(vi, vdev);
> +	if (err)
> +		goto err_find;
> +
>  	virtio_device_ready(vdev);
>  
>  	/* we always have a pending entropy request */
>  	request_entropy(vi);
>  
> +	/* we always have a fill_on_leak request pending */
> +	virtrng_fill_on_leak(vi, vi->leak_data, sizeof(vi->leak_data));
> +
>  	return 0;
>  
>  err_find:
> @@ -246,7 +428,13 @@ static const struct virtio_device_id id_table[] = {
>  	{ 0 },
>  };
>  
> +static unsigned int features[] = {
> +	VIRTIO_RNG_F_LEAK,
> +};
> +
>  static struct virtio_driver virtio_rng_driver = {
> +	.feature_table = features,
> +	.feature_table_size = ARRAY_SIZE(features),
>  	.driver.name =	KBUILD_MODNAME,
>  	.driver.owner =	THIS_MODULE,
>  	.id_table =	id_table,
> diff --git a/include/uapi/linux/virtio_rng.h b/include/uapi/linux/virtio_rng.h
> index c4d5de896f0c..d9774951547e 100644
> --- a/include/uapi/linux/virtio_rng.h
> +++ b/include/uapi/linux/virtio_rng.h
> @@ -5,4 +5,7 @@
>  #include <linux/virtio_ids.h>
>  #include <linux/virtio_config.h>
>  
> +/* The feature bitmap for virtio entropy device */
> +#define VIRTIO_RNG_F_LEAK 0
> +
>  #endif /* _LINUX_VIRTIO_RNG_H */
> -- 
> 2.38.1
> 
> Amazon Spain Services sociedad limitada unipersonal, Calle Ramirez de Prado 5, 28045 Madrid. Registro Mercantil de Madrid . Tomo 22458 . Folio 102 . Hoja M-401234 . CIF B84570936
Babis Chalios Jan. 20, 2023, 12:54 p.m. UTC | #4
On 20/1/23 13:32, Michael S. Tsirkin wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
>
>
>
> On Thu, Jan 19, 2023 at 07:43:47PM +0100, Babis Chalios wrote:
>> Implement the virtio-rng feature that allows a guest driver to request
>> from the device to perform certain operations in the event of an
>> "entropy leak", such as when taking a VM snapshot or restoring a VM from
>> a snapshot. The guest can request one of two operations: (i) fill a
>> buffer with random bytes, or (ii) perform a memory copy between two
>> bytes.
>>
>> The feature is similar to Microsoft's Virtual Machine Generation ID and
>> it can be used to (1) avoid the race-condition that exists in our
>> current VMGENID implementation, between the time vcpus are resumed and
>> the ACPI notification is being handled and (2) provide mechanisms for
>> notifying user-space about snapshot-related events.
>>
>> This commit implements the protocol between guest and device.
>> Additionally, it makes sure there is always a request for random bytes
>> in the event of entropy leak in-flight. Once such an event is observed,
>> the driver feeds these bytes to as entropy using
>> `add_device_randomness`.
>>
>> Keep in mind that this commit does not solve the race-condition issue,
>> it adds fresh entropy whenever the driver handles the used buffer from
>> the fill-on-leak request. In order to close the race window, we need to
>> expose some API so that other kernel subsystems can request directly
>> notifications from the device.
>>
>> Signed-off-by: Babis Chalios <bchalios@amazon.es>
>> ---
>>   drivers/char/hw_random/virtio-rng.c | 200 +++++++++++++++++++++++++++-
>>   include/uapi/linux/virtio_rng.h     |   3 +
>>   2 files changed, 197 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
>> index a6f3a8a2aca6..389a091a8801 100644
>> --- a/drivers/char/hw_random/virtio-rng.c
>> +++ b/drivers/char/hw_random/virtio-rng.c
>> @@ -4,12 +4,14 @@
>>    *  Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
>>    */
>>
>> +#include "asm-generic/errno.h"
> Why are you pulling this in?
> If you really need errno the thing to include
> is linux/errno.h
>
> checkpatch has a rule to catch such cases:
>
> # warn if <asm/foo.h> is #included and <linux/foo.h> is available and includes
> # itself <asm/foo.h> (uses RAW line)
>
> did you run checkpatch?
>
You are right, this is wrong. I think my LSP client pulled this in and I 
missed it because, strangely enough, I did ran
checkpatch but it didn't complain about it.

>>   #include <linux/err.h>
>>   #include <linux/hw_random.h>
>>   #include <linux/scatterlist.h>
>>   #include <linux/spinlock.h>
>>   #include <linux/virtio.h>
>>   #include <linux/virtio_rng.h>
>> +#include <linux/random.h>
>>   #include <linux/module.h>
>>   #include <linux/slab.h>
>>
>> @@ -18,6 +20,12 @@ static DEFINE_IDA(rng_index_ida);
>>   struct virtrng_info {
>>        struct hwrng hwrng;
>>        struct virtqueue *vq;
>> +     /* Leak queues */
>> +     bool has_leakqs;
>> +     struct virtqueue *leakq[2];
>> +     spinlock_t lock;
>> +     int active_leakq;
>> +
>>        char name[25];
>>        int index;
>>        bool hwrng_register_done;
>> @@ -29,27 +37,159 @@ struct virtrng_info {
>>        /* minimal size returned by rng_buffer_size() */
>>   #if SMP_CACHE_BYTES < 32
>>        u8 data[32];
>> +     u8 leak_data[32];
>>   #else
>>        u8 data[SMP_CACHE_BYTES];
>> +     u8 leak_data[SMP_CACHE_BYTES];
>>   #endif
>>   };
>>
>> +/* Swaps the queues and returns the new active leak queue. */
>> +static struct virtqueue *swap_leakqs(struct virtrng_info *vi)
>> +{
>> +     vi->active_leakq = 1 - vi->active_leakq;
>> +     return vi->leakq[vi->active_leakq];
>> +}
>> +
>> +static struct virtqueue *get_active_leakq(struct virtrng_info *vi)
>> +{
>> +     return vi->leakq[vi->active_leakq];
>> +}
>> +
>> +int add_fill_on_leak_request(struct virtrng_info *vi, struct virtqueue *vq, void *data, size_t len)
>> +{
>> +     struct scatterlist sg;
>> +     int ret;
>> +
>> +     sg_init_one(&sg, data, len);
>> +     ret = virtqueue_add_inbuf(vq, &sg, 1, data, GFP_KERNEL);
>> +     if (ret)
>> +             goto err;
>> +
>> +err:
>> +     return ret;
>> +}
>> +
>> +int virtrng_fill_on_leak(struct virtrng_info *vi, void *data, size_t len)
>> +{
>> +     struct virtqueue *vq;
>> +     unsigned long flags;
>> +     int ret;
>> +
>> +     if (!vi->has_leakqs)
>> +             return -EOPNOTSUPP;
>> +
>> +     spin_lock_irqsave(&vi->lock, flags);
>> +
>> +     vq = get_active_leakq(vi);
>> +     ret = add_fill_on_leak_request(vi, vq, data, len);
>> +     if (ret)
>> +             virtqueue_kick(vq);
>> +
>> +     spin_unlock_irqrestore(&vi->lock, flags);
>> +
>> +     return ret;
>> +}
>> +
>> +int add_copy_on_leak_request(struct virtrng_info *vi, struct virtqueue *vq,
>> +             void *to, void *from, size_t len)
>> +{
>> +     int ret;
>> +     struct scatterlist out, in, *sgs[2];
>> +
>> +     sg_init_one(&out, from, len);
>> +     sgs[0] = &out;
>> +     sg_init_one(&in, to, len);
>> +     sgs[1] = &in;
>> +
>> +     ret = virtqueue_add_sgs(vq, sgs, 1, 1, to, GFP_KERNEL);
>> +     if (ret)
>> +             goto err;
>> +
>> +err:
>> +     return ret;
>> +}
>> +
>> +int virtrng_copy_on_leak(struct virtrng_info *vi, void *to, void *from, size_t len)
>> +{
>> +     struct virtqueue *vq;
>> +     unsigned long flags;
>> +     int ret;
>> +
>> +     if (!vi->has_leakqs)
>> +             return -EOPNOTSUPP;
>> +
>> +     spin_lock_irqsave(&vi->lock, flags);
>> +
>> +     vq = get_active_leakq(vi);
>> +     ret = add_copy_on_leak_request(vi, vq, to, from, len);
>> +     if (ret)
>> +             virtqueue_kick(vq);
>> +
>> +     spin_unlock_irqrestore(&vi->lock, flags);
>> +
>> +     return ret;
>> +}
>> +
>> +static void entropy_leak_detected(struct virtqueue *vq)
>> +{
>> +     struct virtrng_info *vi = vq->vdev->priv;
>> +     struct virtqueue *activeq;
>> +     unsigned int len;
>> +     unsigned long flags;
>> +     void *buffer;
>> +     bool kick_activeq = false;
>> +
>> +     spin_lock_irqsave(&vi->lock, flags);
>> +
>> +     activeq = get_active_leakq(vi);
>> +     /* Drain all the used buffers from the queue */
>> +     while ((buffer = virtqueue_get_buf(vq, &len)) != NULL) {
>> +             if (vq == activeq) {
>> +                     pr_debug("%s: entropy leak detected!", vi->name);
>> +                     activeq = swap_leakqs(vi);
>> +             }
>> +
>> +             if (buffer == vi->leak_data) {
>> +                     add_device_randomness(vi->leak_data, sizeof(vi->leak_data));
>> +
>> +                     /* Ensure we always have a pending request for random bytes on entropy
>> +                      * leak. Do it here, after we have swapped leak queues, so it gets handled
>> +                      * with the next entropy leak event.
>> +                      */
>> +                     add_fill_on_leak_request(vi, activeq, vi->leak_data, sizeof(vi->leak_data));
>> +                     kick_activeq = true;
>> +             }
>> +     }
>> +
>> +     if (kick_activeq)
>> +             virtqueue_kick(activeq);
>> +
>> +     spin_unlock_irqrestore(&vi->lock, flags);
>> +}
>> +
>>   static void random_recv_done(struct virtqueue *vq)
>>   {
>>        struct virtrng_info *vi = vq->vdev->priv;
>> +     unsigned long flags;
>>
>> +     spin_lock_irqsave(&vi->lock, flags);
>>        /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
>>        if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
>> -             return;
>> +             goto unlock;
>>
>>        vi->data_idx = 0;
>>
>>        complete(&vi->have_data);
>> +
>> +unlock:
>> +     spin_unlock_irqrestore(&vi->lock, flags);
>>   }
>>
>>   static void request_entropy(struct virtrng_info *vi)
>>   {
>>        struct scatterlist sg;
>> +     unsigned long flags;
>>
>>        reinit_completion(&vi->have_data);
>>        vi->data_avail = 0;
>> @@ -57,10 +197,12 @@ static void request_entropy(struct virtrng_info *vi)
>>
>>        sg_init_one(&sg, vi->data, sizeof(vi->data));
>>
>> +     spin_lock_irqsave(&vi->lock, flags);
>>        /* There should always be room for one buffer. */
>>        virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL);
>>
>>        virtqueue_kick(vi->vq);
>> +     spin_unlock_irqrestore(&vi->lock, flags);
>>   }
>>
>>   static unsigned int copy_data(struct virtrng_info *vi, void *buf,
>> @@ -126,6 +268,40 @@ static void virtio_cleanup(struct hwrng *rng)
>>        complete(&vi->have_data);
>>   }
>>
>> +static int init_virtqueues(struct virtrng_info *vi, struct virtio_device *vdev)
>> +{
>> +     int ret = -ENOMEM, total_vqs = 1;
>> +     struct virtqueue *vqs[3];
>> +     const char *names[3];
>> +     vq_callback_t *callbacks[3];
>> +
>> +     if (vi->has_leakqs)
>> +             total_vqs = 3;
>> +
>> +     callbacks[0] = random_recv_done;
>> +     names[0] = "input";
>> +     if (vi->has_leakqs) {
>> +             callbacks[1] = entropy_leak_detected;
>> +             names[1] = "leakq.1";
>> +             callbacks[2] = entropy_leak_detected;
>> +             names[2] = "leakq.2";
>> +     }
>> +
>> +     ret = virtio_find_vqs(vdev, total_vqs, vqs, callbacks, names, NULL);
>> +     if (ret)
>> +             goto err;
>> +
>> +     vi->vq = vqs[0];
>> +
>> +     if (vi->has_leakqs) {
>> +             vi->leakq[0] = vqs[1];
>> +             vi->leakq[1] = vqs[2];
>> +     }
>> +
>> +err:
>> +     return ret;
>> +}
>> +
>>   static int probe_common(struct virtio_device *vdev)
>>   {
>>        int err, index;
>> @@ -152,18 +328,24 @@ static int probe_common(struct virtio_device *vdev)
>>        };
>>        vdev->priv = vi;
>>
>> -     /* We expect a single virtqueue. */
>> -     vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
>> -     if (IS_ERR(vi->vq)) {
>> -             err = PTR_ERR(vi->vq);
>> -             goto err_find;
>> +     vi->has_leakqs = virtio_has_feature(vdev, VIRTIO_RNG_F_LEAK);
>> +     if (vi->has_leakqs) {
>> +             spin_lock_init(&vi->lock);
>> +             vi->active_leakq = 0;
>>        }
>>
>> +     err = init_virtqueues(vi, vdev);
>> +     if (err)
>> +             goto err_find;
>> +
>>        virtio_device_ready(vdev);
>>
>>        /* we always have a pending entropy request */
>>        request_entropy(vi);
>>
>> +     /* we always have a fill_on_leak request pending */
>> +     virtrng_fill_on_leak(vi, vi->leak_data, sizeof(vi->leak_data));
>> +
>>        return 0;
>>
>>   err_find:
>> @@ -246,7 +428,13 @@ static const struct virtio_device_id id_table[] = {
>>        { 0 },
>>   };
>>
>> +static unsigned int features[] = {
>> +     VIRTIO_RNG_F_LEAK,
>> +};
>> +
>>   static struct virtio_driver virtio_rng_driver = {
>> +     .feature_table = features,
>> +     .feature_table_size = ARRAY_SIZE(features),
>>        .driver.name =  KBUILD_MODNAME,
>>        .driver.owner = THIS_MODULE,
>>        .id_table =     id_table,
>> diff --git a/include/uapi/linux/virtio_rng.h b/include/uapi/linux/virtio_rng.h
>> index c4d5de896f0c..d9774951547e 100644
>> --- a/include/uapi/linux/virtio_rng.h
>> +++ b/include/uapi/linux/virtio_rng.h
>> @@ -5,4 +5,7 @@
>>   #include <linux/virtio_ids.h>
>>   #include <linux/virtio_config.h>
>>
>> +/* The feature bitmap for virtio entropy device */
>> +#define VIRTIO_RNG_F_LEAK 0
>> +
>>   #endif /* _LINUX_VIRTIO_RNG_H */
>> --
>> 2.38.1
>>
>> Amazon Spain Services sociedad limitada unipersonal, Calle Ramirez de Prado 5, 28045 Madrid. Registro Mercantil de Madrid . Tomo 22458 . Folio 102 . Hoja M-401234 . CIF B84570936

Amazon Spain Services sociedad limitada unipersonal, Calle Ramirez de Prado 5, 28045 Madrid. Registro Mercantil de Madrid . Tomo 22458 . Folio 102 . Hoja M-401234 . CIF B84570936
Elliott, Robert (Servers) Jan. 20, 2023, 3:07 p.m. UTC | #5
> > +#include "asm-generic/errno.h"
> 
> Why are you pulling this in?
> If you really need errno the thing to include
> is linux/errno.h
> 
> checkpatch has a rule to catch such cases:
> 
> # warn if <asm/foo.h> is #included and <linux/foo.h> is available and includes
> # itself <asm/foo.h> (uses RAW line)

It's only looking for asm, not variations like asm-generic.
diff mbox series

Patch

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index a6f3a8a2aca6..389a091a8801 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -4,12 +4,14 @@ 
  *  Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
  */
 
+#include "asm-generic/errno.h"
 #include <linux/err.h>
 #include <linux/hw_random.h>
 #include <linux/scatterlist.h>
 #include <linux/spinlock.h>
 #include <linux/virtio.h>
 #include <linux/virtio_rng.h>
+#include <linux/random.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 
@@ -18,6 +20,12 @@  static DEFINE_IDA(rng_index_ida);
 struct virtrng_info {
 	struct hwrng hwrng;
 	struct virtqueue *vq;
+	/* Leak queues */
+	bool has_leakqs;
+	struct virtqueue *leakq[2];
+	spinlock_t lock;
+	int active_leakq;
+
 	char name[25];
 	int index;
 	bool hwrng_register_done;
@@ -29,27 +37,159 @@  struct virtrng_info {
 	/* minimal size returned by rng_buffer_size() */
 #if SMP_CACHE_BYTES < 32
 	u8 data[32];
+	u8 leak_data[32];
 #else
 	u8 data[SMP_CACHE_BYTES];
+	u8 leak_data[SMP_CACHE_BYTES];
 #endif
 };
 
+/* Swaps the queues and returns the new active leak queue. */
+static struct virtqueue *swap_leakqs(struct virtrng_info *vi)
+{
+	vi->active_leakq = 1 - vi->active_leakq;
+	return vi->leakq[vi->active_leakq];
+}
+
+static struct virtqueue *get_active_leakq(struct virtrng_info *vi)
+{
+	return vi->leakq[vi->active_leakq];
+}
+
+int add_fill_on_leak_request(struct virtrng_info *vi, struct virtqueue *vq, void *data, size_t len)
+{
+	struct scatterlist sg;
+	int ret;
+
+	sg_init_one(&sg, data, len);
+	ret = virtqueue_add_inbuf(vq, &sg, 1, data, GFP_KERNEL);
+	if (ret)
+		goto err;
+
+err:
+	return ret;
+}
+
+int virtrng_fill_on_leak(struct virtrng_info *vi, void *data, size_t len)
+{
+	struct virtqueue *vq;
+	unsigned long flags;
+	int ret;
+
+	if (!vi->has_leakqs)
+		return -EOPNOTSUPP;
+
+	spin_lock_irqsave(&vi->lock, flags);
+
+	vq = get_active_leakq(vi);
+	ret = add_fill_on_leak_request(vi, vq, data, len);
+	if (ret)
+		virtqueue_kick(vq);
+
+	spin_unlock_irqrestore(&vi->lock, flags);
+
+	return ret;
+}
+
+int add_copy_on_leak_request(struct virtrng_info *vi, struct virtqueue *vq,
+		void *to, void *from, size_t len)
+{
+	int ret;
+	struct scatterlist out, in, *sgs[2];
+
+	sg_init_one(&out, from, len);
+	sgs[0] = &out;
+	sg_init_one(&in, to, len);
+	sgs[1] = &in;
+
+	ret = virtqueue_add_sgs(vq, sgs, 1, 1, to, GFP_KERNEL);
+	if (ret)
+		goto err;
+
+err:
+	return ret;
+}
+
+int virtrng_copy_on_leak(struct virtrng_info *vi, void *to, void *from, size_t len)
+{
+	struct virtqueue *vq;
+	unsigned long flags;
+	int ret;
+
+	if (!vi->has_leakqs)
+		return -EOPNOTSUPP;
+
+	spin_lock_irqsave(&vi->lock, flags);
+
+	vq = get_active_leakq(vi);
+	ret = add_copy_on_leak_request(vi, vq, to, from, len);
+	if (ret)
+		virtqueue_kick(vq);
+
+	spin_unlock_irqrestore(&vi->lock, flags);
+
+	return ret;
+}
+
+static void entropy_leak_detected(struct virtqueue *vq)
+{
+	struct virtrng_info *vi = vq->vdev->priv;
+	struct virtqueue *activeq;
+	unsigned int len;
+	unsigned long flags;
+	void *buffer;
+	bool kick_activeq = false;
+
+	spin_lock_irqsave(&vi->lock, flags);
+
+	activeq = get_active_leakq(vi);
+	/* Drain all the used buffers from the queue */
+	while ((buffer = virtqueue_get_buf(vq, &len)) != NULL) {
+		if (vq == activeq) {
+			pr_debug("%s: entropy leak detected!", vi->name);
+			activeq = swap_leakqs(vi);
+		}
+
+		if (buffer == vi->leak_data) {
+			add_device_randomness(vi->leak_data, sizeof(vi->leak_data));
+
+			/* Ensure we always have a pending request for random bytes on entropy
+			 * leak. Do it here, after we have swapped leak queues, so it gets handled
+			 * with the next entropy leak event.
+			 */
+			add_fill_on_leak_request(vi, activeq, vi->leak_data, sizeof(vi->leak_data));
+			kick_activeq = true;
+		}
+	}
+
+	if (kick_activeq)
+		virtqueue_kick(activeq);
+
+	spin_unlock_irqrestore(&vi->lock, flags);
+}
+
 static void random_recv_done(struct virtqueue *vq)
 {
 	struct virtrng_info *vi = vq->vdev->priv;
+	unsigned long flags;
 
+	spin_lock_irqsave(&vi->lock, flags);
 	/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
 	if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
-		return;
+		goto unlock;
 
 	vi->data_idx = 0;
 
 	complete(&vi->have_data);
+
+unlock:
+	spin_unlock_irqrestore(&vi->lock, flags);
 }
 
 static void request_entropy(struct virtrng_info *vi)
 {
 	struct scatterlist sg;
+	unsigned long flags;
 
 	reinit_completion(&vi->have_data);
 	vi->data_avail = 0;
@@ -57,10 +197,12 @@  static void request_entropy(struct virtrng_info *vi)
 
 	sg_init_one(&sg, vi->data, sizeof(vi->data));
 
+	spin_lock_irqsave(&vi->lock, flags);
 	/* There should always be room for one buffer. */
 	virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL);
 
 	virtqueue_kick(vi->vq);
+	spin_unlock_irqrestore(&vi->lock, flags);
 }
 
 static unsigned int copy_data(struct virtrng_info *vi, void *buf,
@@ -126,6 +268,40 @@  static void virtio_cleanup(struct hwrng *rng)
 	complete(&vi->have_data);
 }
 
+static int init_virtqueues(struct virtrng_info *vi, struct virtio_device *vdev)
+{
+	int ret = -ENOMEM, total_vqs = 1;
+	struct virtqueue *vqs[3];
+	const char *names[3];
+	vq_callback_t *callbacks[3];
+
+	if (vi->has_leakqs)
+		total_vqs = 3;
+
+	callbacks[0] = random_recv_done;
+	names[0] = "input";
+	if (vi->has_leakqs) {
+		callbacks[1] = entropy_leak_detected;
+		names[1] = "leakq.1";
+		callbacks[2] = entropy_leak_detected;
+		names[2] = "leakq.2";
+	}
+
+	ret = virtio_find_vqs(vdev, total_vqs, vqs, callbacks, names, NULL);
+	if (ret)
+		goto err;
+
+	vi->vq = vqs[0];
+
+	if (vi->has_leakqs) {
+		vi->leakq[0] = vqs[1];
+		vi->leakq[1] = vqs[2];
+	}
+
+err:
+	return ret;
+}
+
 static int probe_common(struct virtio_device *vdev)
 {
 	int err, index;
@@ -152,18 +328,24 @@  static int probe_common(struct virtio_device *vdev)
 	};
 	vdev->priv = vi;
 
-	/* We expect a single virtqueue. */
-	vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
-	if (IS_ERR(vi->vq)) {
-		err = PTR_ERR(vi->vq);
-		goto err_find;
+	vi->has_leakqs = virtio_has_feature(vdev, VIRTIO_RNG_F_LEAK);
+	if (vi->has_leakqs) {
+		spin_lock_init(&vi->lock);
+		vi->active_leakq = 0;
 	}
 
+	err = init_virtqueues(vi, vdev);
+	if (err)
+		goto err_find;
+
 	virtio_device_ready(vdev);
 
 	/* we always have a pending entropy request */
 	request_entropy(vi);
 
+	/* we always have a fill_on_leak request pending */
+	virtrng_fill_on_leak(vi, vi->leak_data, sizeof(vi->leak_data));
+
 	return 0;
 
 err_find:
@@ -246,7 +428,13 @@  static const struct virtio_device_id id_table[] = {
 	{ 0 },
 };
 
+static unsigned int features[] = {
+	VIRTIO_RNG_F_LEAK,
+};
+
 static struct virtio_driver virtio_rng_driver = {
+	.feature_table = features,
+	.feature_table_size = ARRAY_SIZE(features),
 	.driver.name =	KBUILD_MODNAME,
 	.driver.owner =	THIS_MODULE,
 	.id_table =	id_table,
diff --git a/include/uapi/linux/virtio_rng.h b/include/uapi/linux/virtio_rng.h
index c4d5de896f0c..d9774951547e 100644
--- a/include/uapi/linux/virtio_rng.h
+++ b/include/uapi/linux/virtio_rng.h
@@ -5,4 +5,7 @@ 
 #include <linux/virtio_ids.h>
 #include <linux/virtio_config.h>
 
+/* The feature bitmap for virtio entropy device */
+#define VIRTIO_RNG_F_LEAK 0
+
 #endif /* _LINUX_VIRTIO_RNG_H */