diff mbox series

[1/4] statx: define STATX_ATTR_VERITY

Message ID 20191029204141.145309-2-ebiggers@kernel.org (mailing list archive)
State Accepted
Headers show
Series statx: expose the fs-verity bit | expand

Commit Message

Eric Biggers Oct. 29, 2019, 8:41 p.m. UTC 
From: Eric Biggers <ebiggers@google.com>

Add a statx attribute bit STATX_ATTR_VERITY which will be set if the
file has fs-verity enabled.  This is the statx() equivalent of
FS_VERITY_FL which is returned by FS_IOC_GETFLAGS.

This is useful because it allows applications to check whether a file is
a verity file without opening it.  Opening a verity file can be
expensive because the fsverity_info is set up on open, which involves
parsing metadata and optionally verifying a cryptographic signature.

This is analogous to how various other bits are exposed through both
FS_IOC_GETFLAGS and statx(), e.g. the encrypt bit.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 include/linux/stat.h      | 3 ++-
 include/uapi/linux/stat.h | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

Comments

Andreas Dilger Oct. 30, 2019, 6:26 p.m. UTC | #1 
On Oct 29, 2019, at 2:41 PM, Eric Biggers <ebiggers@kernel.org> wrote:
> 
> From: Eric Biggers <ebiggers@google.com>
> 
> Add a statx attribute bit STATX_ATTR_VERITY which will be set if the
> file has fs-verity enabled.  This is the statx() equivalent of
> FS_VERITY_FL which is returned by FS_IOC_GETFLAGS.
> 
> This is useful because it allows applications to check whether a file is
> a verity file without opening it.  Opening a verity file can be
> expensive because the fsverity_info is set up on open, which involves
> parsing metadata and optionally verifying a cryptographic signature.
> 
> This is analogous to how various other bits are exposed through both
> FS_IOC_GETFLAGS and statx(), e.g. the encrypt bit.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

> ---
> include/linux/stat.h      | 3 ++-
> include/uapi/linux/stat.h | 2 +-
> 2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/stat.h b/include/linux/stat.h
> index 765573dc17d659..528c4baad09146 100644
> --- a/include/linux/stat.h
> +++ b/include/linux/stat.h
> @@ -33,7 +33,8 @@ struct kstat {
> 	 STATX_ATTR_IMMUTABLE |				\
> 	 STATX_ATTR_APPEND |				\
> 	 STATX_ATTR_NODUMP |				\
> -	 STATX_ATTR_ENCRYPTED				\
> +	 STATX_ATTR_ENCRYPTED |				\
> +	 STATX_ATTR_VERITY				\
> 	 )/* Attrs corresponding to FS_*_FL flags */
> 	u64		ino;
> 	dev_t		dev;
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index 7b35e98d3c58b1..ad80a5c885d598 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -167,8 +167,8 @@ struct statx {
> #define STATX_ATTR_APPEND		0x00000020 /* [I] File is append-only */
> #define STATX_ATTR_NODUMP		0x00000040 /* [I] File is not to be dumped */
> #define STATX_ATTR_ENCRYPTED		0x00000800 /* [I] File requires key to decrypt in fs */
> -
> #define STATX_ATTR_AUTOMOUNT		0x00001000 /* Dir: Automount trigger */
> +#define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */
> 
> 
> #endif /* _UAPI_LINUX_STAT_H */
> --
> 2.24.0.rc1.363.gb1bccd3e3d-goog
> 


Cheers, Andreas
Darrick J. Wong Nov. 7, 2019, 1:44 a.m. UTC | #2 
On Tue, Oct 29, 2019 at 01:41:38PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Add a statx attribute bit STATX_ATTR_VERITY which will be set if the
> file has fs-verity enabled.  This is the statx() equivalent of
> FS_VERITY_FL which is returned by FS_IOC_GETFLAGS.
> 
> This is useful because it allows applications to check whether a file is
> a verity file without opening it.  Opening a verity file can be
> expensive because the fsverity_info is set up on open, which involves
> parsing metadata and optionally verifying a cryptographic signature.
> 
> This is analogous to how various other bits are exposed through both
> FS_IOC_GETFLAGS and statx(), e.g. the encrypt bit.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  include/linux/stat.h      | 3 ++-
>  include/uapi/linux/stat.h | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/stat.h b/include/linux/stat.h
> index 765573dc17d659..528c4baad09146 100644
> --- a/include/linux/stat.h
> +++ b/include/linux/stat.h
> @@ -33,7 +33,8 @@ struct kstat {
>  	 STATX_ATTR_IMMUTABLE |				\
>  	 STATX_ATTR_APPEND |				\
>  	 STATX_ATTR_NODUMP |				\
> -	 STATX_ATTR_ENCRYPTED				\
> +	 STATX_ATTR_ENCRYPTED |				\
> +	 STATX_ATTR_VERITY				\
>  	 )/* Attrs corresponding to FS_*_FL flags */
>  	u64		ino;
>  	dev_t		dev;
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index 7b35e98d3c58b1..ad80a5c885d598 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -167,8 +167,8 @@ struct statx {
>  #define STATX_ATTR_APPEND		0x00000020 /* [I] File is append-only */
>  #define STATX_ATTR_NODUMP		0x00000040 /* [I] File is not to be dumped */
>  #define STATX_ATTR_ENCRYPTED		0x00000800 /* [I] File requires key to decrypt in fs */
> -
>  #define STATX_ATTR_AUTOMOUNT		0x00001000 /* Dir: Automount trigger */
> +#define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */

Any reason why this wasn't 0x2000?

If there's a manpage update that goes with this, then...
Acked-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

>  
>  
>  #endif /* _UAPI_LINUX_STAT_H */
> -- 
> 2.24.0.rc1.363.gb1bccd3e3d-goog
>
Andreas Dilger Nov. 7, 2019, 2:05 a.m. UTC | #3 
On Nov 6, 2019, at 6:44 PM, Darrick J. Wong <darrick.wong@oracle.com> wrote:
> 
> On Tue, Oct 29, 2019 at 01:41:38PM -0700, Eric Biggers wrote:
>> From: Eric Biggers <ebiggers@google.com>
>> 
>> Add a statx attribute bit STATX_ATTR_VERITY which will be set if the
>> file has fs-verity enabled.  This is the statx() equivalent of
>> FS_VERITY_FL which is returned by FS_IOC_GETFLAGS.
>> 
>> This is useful because it allows applications to check whether a file is
>> a verity file without opening it.  Opening a verity file can be
>> expensive because the fsverity_info is set up on open, which involves
>> parsing metadata and optionally verifying a cryptographic signature.
>> 
>> This is analogous to how various other bits are exposed through both
>> FS_IOC_GETFLAGS and statx(), e.g. the encrypt bit.
>> 
>> Signed-off-by: Eric Biggers <ebiggers@google.com>
>> ---
>> include/linux/stat.h      | 3 ++-
>> include/uapi/linux/stat.h | 2 +-
>> 2 files changed, 3 insertions(+), 2 deletions(-)
>> 
>> diff --git a/include/linux/stat.h b/include/linux/stat.h
>> index 765573dc17d659..528c4baad09146 100644
>> --- a/include/linux/stat.h
>> +++ b/include/linux/stat.h
>> @@ -33,7 +33,8 @@ struct kstat {
>> 	 STATX_ATTR_IMMUTABLE |				\
>> 	 STATX_ATTR_APPEND |				\
>> 	 STATX_ATTR_NODUMP |				\
>> -	 STATX_ATTR_ENCRYPTED				\
>> +	 STATX_ATTR_ENCRYPTED |				\
>> +	 STATX_ATTR_VERITY				\
>> 	 )/* Attrs corresponding to FS_*_FL flags */
>> 	u64		ino;
>> 	dev_t		dev;
>> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
>> index 7b35e98d3c58b1..ad80a5c885d598 100644
>> --- a/include/uapi/linux/stat.h
>> +++ b/include/uapi/linux/stat.h
>> @@ -167,8 +167,8 @@ struct statx {
>> #define STATX_ATTR_APPEND		0x00000020 /* [I] File is append-only */
>> #define STATX_ATTR_NODUMP		0x00000040 /* [I] File is not to be dumped */
>> #define STATX_ATTR_ENCRYPTED		0x00000800 /* [I] File requires key to decrypt in fs */
>> -
>> #define STATX_ATTR_AUTOMOUNT		0x00001000 /* Dir: Automount trigger */
>> +#define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */
> 
> Any reason why this wasn't 0x2000?

A few lines earlier in this file it states:

 * Note that the flags marked [I] correspond to generic FS_IOC_FLAGS
 * semantically.  Where possible, the numerical value is picked to
 * correspond also.

Cheers, Andreas
Eric Biggers Nov. 7, 2019, 10:12 p.m. UTC | #4 
On Wed, Nov 06, 2019 at 05:44:20PM -0800, Darrick J. Wong wrote:
> On Tue, Oct 29, 2019 at 01:41:38PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > Add a statx attribute bit STATX_ATTR_VERITY which will be set if the
> > file has fs-verity enabled.  This is the statx() equivalent of
> > FS_VERITY_FL which is returned by FS_IOC_GETFLAGS.
> > 
> > This is useful because it allows applications to check whether a file is
> > a verity file without opening it.  Opening a verity file can be
> > expensive because the fsverity_info is set up on open, which involves
> > parsing metadata and optionally verifying a cryptographic signature.
> > 
> > This is analogous to how various other bits are exposed through both
> > FS_IOC_GETFLAGS and statx(), e.g. the encrypt bit.
> > 
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > ---
> >  include/linux/stat.h      | 3 ++-
> >  include/uapi/linux/stat.h | 2 +-
> >  2 files changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/stat.h b/include/linux/stat.h
> > index 765573dc17d659..528c4baad09146 100644
> > --- a/include/linux/stat.h
> > +++ b/include/linux/stat.h
> > @@ -33,7 +33,8 @@ struct kstat {
> >  	 STATX_ATTR_IMMUTABLE |				\
> >  	 STATX_ATTR_APPEND |				\
> >  	 STATX_ATTR_NODUMP |				\
> > -	 STATX_ATTR_ENCRYPTED				\
> > +	 STATX_ATTR_ENCRYPTED |				\
> > +	 STATX_ATTR_VERITY				\
> >  	 )/* Attrs corresponding to FS_*_FL flags */
> >  	u64		ino;
> >  	dev_t		dev;
> > diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> > index 7b35e98d3c58b1..ad80a5c885d598 100644
> > --- a/include/uapi/linux/stat.h
> > +++ b/include/uapi/linux/stat.h
> > @@ -167,8 +167,8 @@ struct statx {
> >  #define STATX_ATTR_APPEND		0x00000020 /* [I] File is append-only */
> >  #define STATX_ATTR_NODUMP		0x00000040 /* [I] File is not to be dumped */
> >  #define STATX_ATTR_ENCRYPTED		0x00000800 /* [I] File requires key to decrypt in fs */
> > -
> >  #define STATX_ATTR_AUTOMOUNT		0x00001000 /* Dir: Automount trigger */
> > +#define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */
> 
> Any reason why this wasn't 0x2000?

Yes, as Andreas pointed out, the value is chosen to match the corresponding
FS_IOC_GETFLAGS bit, like the other bits above marked [I].

> 
> If there's a manpage update that goes with this, then...
> Acked-by: Darrick J. Wong <darrick.wong@oracle.com>
> 

It's pretty trivial to add it to the statx(2) man page.
I've sent out a patch for comment:
https://lkml.kernel.org/linux-fscrypt/20191107220248.32025-1-ebiggers@kernel.org/

- Eric
diff mbox series

Patch

diff --git a/include/linux/stat.h b/include/linux/stat.h
index 765573dc17d659..528c4baad09146 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -33,7 +33,8 @@  struct kstat {
 	 STATX_ATTR_IMMUTABLE |				\
 	 STATX_ATTR_APPEND |				\
 	 STATX_ATTR_NODUMP |				\
-	 STATX_ATTR_ENCRYPTED				\
+	 STATX_ATTR_ENCRYPTED |				\
+	 STATX_ATTR_VERITY				\
 	 )/* Attrs corresponding to FS_*_FL flags */
 	u64		ino;
 	dev_t		dev;
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 7b35e98d3c58b1..ad80a5c885d598 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -167,8 +167,8 @@  struct statx {
 #define STATX_ATTR_APPEND		0x00000020 /* [I] File is append-only */
 #define STATX_ATTR_NODUMP		0x00000040 /* [I] File is not to be dumped */
 #define STATX_ATTR_ENCRYPTED		0x00000800 /* [I] File requires key to decrypt in fs */
-
 #define STATX_ATTR_AUTOMOUNT		0x00001000 /* Dir: Automount trigger */
+#define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */
 
 
 #endif /* _UAPI_LINUX_STAT_H */