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xfs: fix boundary test in xfs_attr_shortform_verify

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The boundary test for the fixed-offset parts of xfs_attr_sf_entry in
xfs_attr_shortform_verify is off by one, because the variable array
at the end is defined as nameval[1] not nameval[].
Hence we need to subtract 1 from the calculation.

This can be shown by:

# touch file
# setfattr -n root.a file

and verifications will fail when it's written to disk.

This only matters for a last attribute which has a single-byte name
and no value, otherwise the combination of namelen & valuelen will
push endp further out and this test won't fail.

Fixes: 1e1bbd8e7ee06 ("xfs: create structure verifier function for shortform xattrs")
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Eric Sandeen 2020-08-26 14:11:58 -07:00 committed by Darrick J. Wong
parent 657f101930
commit f4020438fa
1 changed files with 3 additions and 1 deletions
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4
fs/xfs/libxfs/xfs_attr_leaf.c
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@ -1036,8 +1036,10 @@ xfs_attr_shortform_verify(
* struct xfs_attr_sf_entry has a variable length.
* Check the fixed-offset parts of the structure are
* within the data buffer.
* xfs_attr_sf_entry is defined with a 1-byte variable
* array at the end, so we must subtract that off.
*/
if (((char *)sfep + sizeof(*sfep)) >= endp)
if (((char *)sfep + sizeof(*sfep) - 1) >= endp)
return __this_address;
/* Don't allow names with known bad length. */