diff mbox series

crypto: crypto_xor - use helpers for unaligned accesses

Message ID 20220215105717.184572-1-ardb@kernel.org (mailing list archive)
State Changes Requested
Delegated to: Herbert Xu
Headers show
Series crypto: crypto_xor - use helpers for unaligned accesses | expand

Commit Message

Ard Biesheuvel Feb. 15, 2022, 10:57 a.m. UTC 
Dereferencing a misaligned pointer is undefined behavior in C, and may
result in codegen on architectures such as ARM that trigger alignments
traps and expensive fixups in software.

Instead, use the get_aligned()/put_aligned() accessors, which are cheap
or even completely free when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y.

In the converse case, the prior alignment checks ensure that the casts
are safe, and so no unaligned accessors are necessary.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 crypto/algapi.c         | 24 +++++++++++++++++++++---
 include/crypto/algapi.h | 11 +++++++++--
 2 files changed, 30 insertions(+), 5 deletions(-)

Comments

kernel test robot Feb. 15, 2022, 1:47 p.m. UTC | #1 
Hi Ard,

I love your patch! Perhaps something to improve:

[auto build test WARNING on herbert-cryptodev-2.6/master]
[also build test WARNING on herbert-crypto-2.6/master v5.17-rc4 next-20220215]
[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]

url:    https://github.com/0day-ci/linux/commits/Ard-Biesheuvel/crypto-crypto_xor-use-helpers-for-unaligned-accesses/20220215-185741
base:   https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git master
config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20220215/202202152134.HZ9sQwkL-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 11.2.0
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/0day-ci/linux/commit/6ca2d09816a67230ab30f3c7e7d87815e833d0af
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Ard-Biesheuvel/crypto-crypto_xor-use-helpers-for-unaligned-accesses/20220215-185741
        git checkout 6ca2d09816a67230ab30f3c7e7d87815e833d0af
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arc SHELL=/bin/bash drivers/md/

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

All warnings (new ones prefixed by >>):

   In file included from arch/arc/include/asm/unaligned.h:11,
                    from arch/arc/include/asm/io.h:12,
                    from include/linux/io.h:13,
                    from include/linux/irq.h:20,
                    from include/asm-generic/hardirq.h:17,
                    from ./arch/arc/include/generated/asm/hardirq.h:1,
                    from include/linux/hardirq.h:11,
                    from include/linux/highmem.h:11,
                    from include/linux/bvec.h:10,
                    from include/linux/blk_types.h:10,
                    from include/linux/bio.h:10,
                    from drivers/md/dm-crypt.c:16:
   In function 'crypto_xor_cpy',
       inlined from 'crypt_iv_tcw_whitening.isra' at drivers/md/dm-crypt.c:645:2:
>> include/asm-generic/unaligned.h:14:15: warning: '*(const struct <anonymous> *)(&buf[0]).x' is used uninitialized [-Wuninitialized]
      14 |         __pptr->x;                                                              \
         |         ~~~~~~^~~
   include/asm-generic/unaligned.h:22:33: note: in expansion of macro '__get_unaligned_t'
      22 | #define get_unaligned(ptr)      __get_unaligned_t(typeof(*(ptr)), (ptr))
         |                                 ^~~~~~~~~~~~~~~~~
   include/crypto/algapi.h:183:29: note: in expansion of macro 'get_unaligned'
     183 |                         l = get_unaligned(d) ^ get_unaligned(s1++)
         |                             ^~~~~~~~~~~~~
   drivers/md/dm-crypt.c: In function 'crypt_iv_tcw_whitening.isra':
   drivers/md/dm-crypt.c:640:12: note: 'buf' declared here
     640 |         u8 buf[TCW_WHITENING_SIZE];
         |            ^~~
   In file included from arch/arc/include/asm/unaligned.h:11,
                    from arch/arc/include/asm/io.h:12,
                    from include/linux/io.h:13,
                    from include/linux/irq.h:20,
                    from include/asm-generic/hardirq.h:17,
                    from ./arch/arc/include/generated/asm/hardirq.h:1,
                    from include/linux/hardirq.h:11,
                    from include/linux/highmem.h:11,
                    from include/linux/bvec.h:10,
                    from include/linux/blk_types.h:10,
                    from include/linux/bio.h:10,
                    from drivers/md/dm-crypt.c:16:
   In function 'crypto_xor_cpy',
       inlined from 'crypt_iv_tcw_whitening.isra' at drivers/md/dm-crypt.c:645:2:
   include/asm-generic/unaligned.h:14:15: warning: '*(const struct <anonymous> *)(&buf[4]).x' is used uninitialized [-Wuninitialized]
      14 |         __pptr->x;                                                              \
         |         ~~~~~~^~~
   include/asm-generic/unaligned.h:22:33: note: in expansion of macro '__get_unaligned_t'
      22 | #define get_unaligned(ptr)      __get_unaligned_t(typeof(*(ptr)), (ptr))
         |                                 ^~~~~~~~~~~~~~~~~
   include/crypto/algapi.h:183:29: note: in expansion of macro 'get_unaligned'
     183 |                         l = get_unaligned(d) ^ get_unaligned(s1++)
         |                             ^~~~~~~~~~~~~
   drivers/md/dm-crypt.c: In function 'crypt_iv_tcw_whitening.isra':
   drivers/md/dm-crypt.c:640:12: note: 'buf' declared here
     640 |         u8 buf[TCW_WHITENING_SIZE];
         |            ^~~
   In file included from arch/arc/include/asm/unaligned.h:11,
                    from arch/arc/include/asm/io.h:12,
                    from include/linux/io.h:13,
                    from include/linux/irq.h:20,
                    from include/asm-generic/hardirq.h:17,
                    from ./arch/arc/include/generated/asm/hardirq.h:1,
                    from include/linux/hardirq.h:11,
                    from include/linux/highmem.h:11,
                    from include/linux/bvec.h:10,
                    from include/linux/blk_types.h:10,
                    from include/linux/bio.h:10,
                    from drivers/md/dm-crypt.c:16:
   In function 'crypto_xor_cpy',
       inlined from 'crypt_iv_tcw_whitening.isra' at drivers/md/dm-crypt.c:646:2:
   include/asm-generic/unaligned.h:14:15: warning: '*(const struct <anonymous> *)(&buf[8]).x' is used uninitialized [-Wuninitialized]
      14 |         __pptr->x;                                                              \
         |         ~~~~~~^~~
   include/asm-generic/unaligned.h:22:33: note: in expansion of macro '__get_unaligned_t'
      22 | #define get_unaligned(ptr)      __get_unaligned_t(typeof(*(ptr)), (ptr))
         |                                 ^~~~~~~~~~~~~~~~~
   include/crypto/algapi.h:183:29: note: in expansion of macro 'get_unaligned'
     183 |                         l = get_unaligned(d) ^ get_unaligned(s1++)
         |                             ^~~~~~~~~~~~~
   drivers/md/dm-crypt.c: In function 'crypt_iv_tcw_whitening.isra':
   drivers/md/dm-crypt.c:640:12: note: 'buf' declared here
     640 |         u8 buf[TCW_WHITENING_SIZE];
         |            ^~~
   In file included from arch/arc/include/asm/unaligned.h:11,
                    from arch/arc/include/asm/io.h:12,
                    from include/linux/io.h:13,
                    from include/linux/irq.h:20,
                    from include/asm-generic/hardirq.h:17,
                    from ./arch/arc/include/generated/asm/hardirq.h:1,
                    from include/linux/hardirq.h:11,
                    from include/linux/highmem.h:11,
                    from include/linux/bvec.h:10,
                    from include/linux/blk_types.h:10,
                    from include/linux/bio.h:10,
                    from drivers/md/dm-crypt.c:16:
   In function 'crypto_xor_cpy',
       inlined from 'crypt_iv_tcw_whitening.isra' at drivers/md/dm-crypt.c:646:2:
   include/asm-generic/unaligned.h:14:15: warning: '*(const struct <anonymous> *)(&buf[12]).x' is used uninitialized [-Wuninitialized]
      14 |         __pptr->x;                                                              \
         |         ~~~~~~^~~
   include/asm-generic/unaligned.h:22:33: note: in expansion of macro '__get_unaligned_t'
      22 | #define get_unaligned(ptr)      __get_unaligned_t(typeof(*(ptr)), (ptr))
         |                                 ^~~~~~~~~~~~~~~~~
   include/crypto/algapi.h:183:29: note: in expansion of macro 'get_unaligned'
     183 |                         l = get_unaligned(d) ^ get_unaligned(s1++)
         |                             ^~~~~~~~~~~~~
   drivers/md/dm-crypt.c: In function 'crypt_iv_tcw_whitening.isra':
   drivers/md/dm-crypt.c:640:12: note: 'buf' declared here
     640 |         u8 buf[TCW_WHITENING_SIZE];
         |            ^~~


vim +14 include/asm-generic/unaligned.h

aafe4dbed0bf6c Arnd Bergmann 2009-05-13  11  
803f4e1eab7a89 Arnd Bergmann 2021-05-08  12  #define __get_unaligned_t(type, ptr) ({						\
803f4e1eab7a89 Arnd Bergmann 2021-05-08  13  	const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);	\
803f4e1eab7a89 Arnd Bergmann 2021-05-08 @14  	__pptr->x;								\
803f4e1eab7a89 Arnd Bergmann 2021-05-08  15  })
803f4e1eab7a89 Arnd Bergmann 2021-05-08  16  

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot Feb. 15, 2022, 5:01 p.m. UTC | #2 
Hi Ard,

I love your patch! Perhaps something to improve:

[auto build test WARNING on herbert-cryptodev-2.6/master]
[also build test WARNING on herbert-crypto-2.6/master v5.17-rc4 next-20220215]
[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]

url:    https://github.com/0day-ci/linux/commits/Ard-Biesheuvel/crypto-crypto_xor-use-helpers-for-unaligned-accesses/20220215-185741
base:   https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git master
config: i386-randconfig-a003 (https://download.01.org/0day-ci/archive/20220216/202202160048.w2jucJCP-lkp@intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/6ca2d09816a67230ab30f3c7e7d87815e833d0af
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Ard-Biesheuvel/crypto-crypto_xor-use-helpers-for-unaligned-accesses/20220215-185741
        git checkout 6ca2d09816a67230ab30f3c7e7d87815e833d0af
        # save the config file to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kernel/ drivers/md/

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

All warnings (new ones prefixed by >>):

   In file included from ./arch/x86/include/generated/asm/unaligned.h:1,
                    from drivers/md/dm-crypt.c:30:
   drivers/md/dm-crypt.c: In function 'crypt_iv_tcw_whitening':
>> include/asm-generic/unaligned.h:14:8: warning: 'buf.x' is used uninitialized in this function [-Wuninitialized]
      14 |  __pptr->x;        \
         |        ^~
>> include/asm-generic/unaligned.h:14:8: warning: '*((void *)&buf+4).x' is used uninitialized in this function [-Wuninitialized]
   include/asm-generic/unaligned.h:14:8: warning: '*((void *)&buf+8).x' is used uninitialized in this function [-Wuninitialized]
   include/asm-generic/unaligned.h:14:8: warning: '*((void *)&buf+12).x' is used uninitialized in this function [-Wuninitialized]


vim +14 include/asm-generic/unaligned.h

aafe4dbed0bf6c Arnd Bergmann 2009-05-13  11  
803f4e1eab7a89 Arnd Bergmann 2021-05-08  12  #define __get_unaligned_t(type, ptr) ({						\
803f4e1eab7a89 Arnd Bergmann 2021-05-08  13  	const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);	\
803f4e1eab7a89 Arnd Bergmann 2021-05-08 @14  	__pptr->x;								\
803f4e1eab7a89 Arnd Bergmann 2021-05-08  15  })
803f4e1eab7a89 Arnd Bergmann 2021-05-08  16  

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Herbert Xu Feb. 23, 2022, 2:50 a.m. UTC | #3 
On Tue, Feb 15, 2022 at 11:57:17AM +0100, Ard Biesheuvel wrote:
> Dereferencing a misaligned pointer is undefined behavior in C, and may
> result in codegen on architectures such as ARM that trigger alignments
> traps and expensive fixups in software.
> 
> Instead, use the get_aligned()/put_aligned() accessors, which are cheap
> or even completely free when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y.
> 
> In the converse case, the prior alignment checks ensure that the casts
> are safe, and so no unaligned accessors are necessary.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  crypto/algapi.c         | 24 +++++++++++++++++++++---
>  include/crypto/algapi.h | 11 +++++++++--
>  2 files changed, 30 insertions(+), 5 deletions(-)

Ard, could you please take a look at the two kbuild reports and
see if there is an issue that needs to be resolved?

Thanks,
Ard Biesheuvel Feb. 23, 2022, 6:44 a.m. UTC | #4 
On Wed, 23 Feb 2022 at 03:50, Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Tue, Feb 15, 2022 at 11:57:17AM +0100, Ard Biesheuvel wrote:
> > Dereferencing a misaligned pointer is undefined behavior in C, and may
> > result in codegen on architectures such as ARM that trigger alignments
> > traps and expensive fixups in software.
> >
> > Instead, use the get_aligned()/put_aligned() accessors, which are cheap
> > or even completely free when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y.
> >
> > In the converse case, the prior alignment checks ensure that the casts
> > are safe, and so no unaligned accessors are necessary.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >  crypto/algapi.c         | 24 +++++++++++++++++++++---
> >  include/crypto/algapi.h | 11 +++++++++--
> >  2 files changed, 30 insertions(+), 5 deletions(-)
>
> Ard, could you please take a look at the two kbuild reports and
> see if there is an issue that needs to be resolved?
>

My patch is flawed - I'll fix it and send a v2.
diff mbox series

Patch

diff --git a/crypto/algapi.c b/crypto/algapi.c
index 76fdaa16bd4a..5f96ac51269a 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -1002,7 +1002,13 @@  void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int len)
 	}
 
 	while (IS_ENABLED(CONFIG_64BIT) && len >= 8 && !(relalign & 7)) {
-		*(u64 *)dst = *(u64 *)src1 ^  *(u64 *)src2;
+		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
+			u64 l = get_unaligned((u64 *)src1) ^
+				get_unaligned((u64 *)src2);
+			put_unaligned(l, (u64 *)dst);
+		} else {
+			*(u64 *)dst = *(u64 *)src1 ^ *(u64 *)src2;
+		}
 		dst += 8;
 		src1 += 8;
 		src2 += 8;
@@ -1010,7 +1016,13 @@  void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int len)
 	}
 
 	while (len >= 4 && !(relalign & 3)) {
-		*(u32 *)dst = *(u32 *)src1 ^ *(u32 *)src2;
+		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
+			u32 l = get_unaligned((u32 *)src1) ^
+				get_unaligned((u32 *)src2);
+			put_unaligned(l, (u32 *)dst);
+		} else {
+			*(u32 *)dst = *(u32 *)src1 ^ *(u32 *)src2;
+		}
 		dst += 4;
 		src1 += 4;
 		src2 += 4;
@@ -1018,7 +1030,13 @@  void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int len)
 	}
 
 	while (len >= 2 && !(relalign & 1)) {
-		*(u16 *)dst = *(u16 *)src1 ^ *(u16 *)src2;
+		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
+			u16 l = get_unaligned((u16 *)src1) ^
+				get_unaligned((u16 *)src2);
+			put_unaligned(l, (u16 *)dst);
+		} else {
+			*(u16 *)dst = *(u16 *)src1 ^ *(u16 *)src2;
+		}
 		dst += 2;
 		src1 += 2;
 		src2 += 2;
diff --git a/include/crypto/algapi.h b/include/crypto/algapi.h
index f76ec723ceae..932ae31b0b4d 100644
--- a/include/crypto/algapi.h
+++ b/include/crypto/algapi.h
@@ -13,6 +13,8 @@ 
 #include <linux/list.h>
 #include <linux/types.h>
 
+#include <asm/unaligned.h>
+
 /*
  * Maximum values for blocksize and alignmask, used to allocate
  * static buffers that are big enough for any combination of
@@ -154,9 +156,11 @@  static inline void crypto_xor(u8 *dst, const u8 *src, unsigned int size)
 	    (size % sizeof(unsigned long)) == 0) {
 		unsigned long *d = (unsigned long *)dst;
 		unsigned long *s = (unsigned long *)src;
+		unsigned long l;
 
 		while (size > 0) {
-			*d++ ^= *s++;
+			l = get_unaligned(d) ^ get_unaligned(s++);
+			put_unaligned(l, d++);
 			size -= sizeof(unsigned long);
 		}
 	} else {
@@ -173,9 +177,12 @@  static inline void crypto_xor_cpy(u8 *dst, const u8 *src1, const u8 *src2,
 		unsigned long *d = (unsigned long *)dst;
 		unsigned long *s1 = (unsigned long *)src1;
 		unsigned long *s2 = (unsigned long *)src2;
+		unsigned long l;
 
 		while (size > 0) {
-			*d++ = *s1++ ^ *s2++;
+			l = get_unaligned(d) ^ get_unaligned(s1++)
+			  ^ get_unaligned(s2++);
+			put_unaligned(l, d++);
 			size -= sizeof(unsigned long);
 		}
 	} else {