Re: [PATCH 11/13] fsverity: report validation errors back to the filesystem

Eric Biggers
2024-04-24T18:52:32Z

On Wed, Apr 24, 2024 at 11:18:26AM -0700, Darrick J. Wong wrote:
> On Thu, Apr 04, 2024 at 11:09:11PM -0400, Eric Biggers wrote:
> > On Fri, Mar 29, 2024 at 05:35:32PM -0700, Darrick J. Wong wrote:
> > > + /**
> > > + * Notify the filesystem that file data validation failed
> > > + *
> > > + * @inode: the inode being validated
> > > + * @pos: the file position of the invalid data
> > > + * @len: the length of the invalid data
> > > + *
> > > + * This is called when fs-verity cannot validate the file contents.
> > > + */
> > > + void (*fail_validation)(struct inode *inode, loff_t pos, size_t len);
> >
> > There is a difference between the file actually being corrupt (mismatching
> > hashes) and other problems like disk errors reading from the Merkle tree.
> > "Validation failed" is a bit ambiguous, and "cannot validate the file contents"
> > even more so. Do you want only file corruption errors? If so it may be a good
> > idea to call this 'file_corrupt', which would be consistent with the
> > "FILE CORRUPTED" error message in fs/verity/verify.c. Or do you actually want
> > all errors? Either way, it needs to be clarified what is actually meant.
>
> I only want actual file corruption errors -- XFS can handle disk errors
> from reading merkle tree blocks on its own. I'll change this to
> file_corrupt. How's this?
>
> /**
> * Notify the filesystem that file data is corrupt.
> *
> * @inode: the inode being validated
> * @pos: the file position of the invalid data
> * @len: the length of the invalid data
> *
> * This function is called when fs-verity cannot validate the file
> * contents against the merkle tree hashes and logs a FILE CORRUPTED
> * error message.
> */
> void (*file_corrupt)(struct inode *inode, loff_t pos, size_t len);

It looks good except for the last sentence, which still has the potentially
misleading "cannot validate the file contents" wording. How about something
like the following:

"This function is called when fs-verity detects that a portion of a file's data
is inconsistent with the Merkle tree, or a Merkle tree block needed to validate
the data is inconsistent with the level above it."

- Eric