On Sat, Nov 14, 2020 at 10:02:34PM +0800, Gao Xiang wrote:
Currently, commit e9e2eae89ddb dropped a (int) decoration from XFS_LITINO(mp), and since sizeof() expression is also involved, the result of XFS_LITINO(mp) is simply as the size_t type (commonly unsigned long).
Considering the expression in xfs_attr_shortform_bytesfit(): offset = (XFS_LITINO(mp) - bytes) >> 3; let "bytes" be (int)340, and "XFS_LITINO(mp)" be (unsigned long)336.
on 64-bit platform, the expression is offset = ((unsigned long)336 - (int)340) >> 3 = (int)(0xfffffffffffffffcUL >> 3) = -1
but on 32-bit platform, the expression is offset = ((unsigned long)336 - (int)340) >> 3 = (int)(0xfffffffcUL >> 3) = 0x1fffffff instead.
so offset becomes a large positive number on 32-bit platform, and cause xfs_attr_shortform_bytesfit() returns maxforkoff rather than 0.
Therefore, one result is "ASSERT(new_size <= XFS_IFORK_SIZE(ip, whichfork));"
assertion failure in xfs_idata_realloc(), which was also the root cause of the original bugreport from Dennis, see: https://bugzilla.redhat.com/show_bug.cgi?id=1894177
And it can also be manually triggered with the following commands: $ touch a; $ setfattr -n user.0 -v "`seq 0 80`" a; $ setfattr -n user.1 -v "`seq 0 80`" a
on 32-bit platform.
Fix the case in xfs_attr_shortform_bytesfit() by bailing out "XFS_LITINO(mp) < bytes" in advance suggested by Eric and a misleading comment together with this bugfix suggested by Darrick. It seems the other users of XFS_LITINO(mp) are not impacted.
Fixes: e9e2eae89ddb ("xfs: only check the superblock version for dinode size calculation") Cc: stable@vger.kernel.org # 5.7+ Reported-and-tested-by: Dennis Gilmore dgilmore@redhat.com Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Gao Xiang hsiangkao@redhat.com
Looks good to me, Reviewed-by: Darrick J. Wong darrick.wong@oracle.com
--D
changes since v2:
- collect more tags from the replies of v2;
- refine a comment suggested by Christoph.
fs/xfs/libxfs/xfs_attr_leaf.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c index bb128db220ac..d6ef69ab1c67 100644 --- a/fs/xfs/libxfs/xfs_attr_leaf.c +++ b/fs/xfs/libxfs/xfs_attr_leaf.c @@ -515,7 +515,7 @@ xfs_attr_copy_value( *========================================================================*/ /*
- Query whether the requested number of additional bytes of extended
- Query whether the total requested number of attr fork bytes of extended
- attribute space will be able to fit inline.
- Returns zero if not, else the di_forkoff fork offset to be used in the
@@ -535,6 +535,12 @@ xfs_attr_shortform_bytesfit( int maxforkoff; int offset;
- /*
* Check if the new size could fit at all first:*/- if (bytes > XFS_LITINO(mp))
return 0;- /* rounded down */ offset = (XFS_LITINO(mp) - bytes) >> 3;
2.18.4