Re: [PATCH 1/4] statx: define STATX_ATTR_VERITY

From: Andreas Dilger <adilger@dilger.ca>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Eric Biggers <ebiggers@kernel.org>,
	linux-fscrypt@vger.kernel.org,
	Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
	linux-ext4 <linux-ext4@vger.kernel.org>,
	linux-f2fs-devel@lists.sourceforge.net,
	Linux API <linux-api@vger.kernel.org>,
	David Howells <dhowells@redhat.com>,
	Theodore Ts'o <tytso@mit.edu>, Jaegeuk Kim <jaegeuk@kernel.org>,
	Victor Hsieh <victorhsieh@google.com>
Subject: Re: [PATCH 1/4] statx: define STATX_ATTR_VERITY
Date: Wed, 6 Nov 2019 19:05:38 -0700	[thread overview]
Message-ID: <EFEE536E-B2E7-4AFF-ADCD-8C39F26E9C70@dilger.ca> (raw)
In-Reply-To: <20191107014420.GD15212@magnolia>

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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

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