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xfs: prevent bogus assert when trying to remove non-existent attribute

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If the attribute fork on an inode is in btree format and has
multiple levels (i.e node format rather than leaf format), then a
lookup failure will trigger an assert failure in xfs_da_path_shift
if the flag XFS_DA_OP_OKNOENT is not set. This flag is used to
indicate to the directory btree code that not finding an entry is
not a fatal error. In the case of doing a lookup for a directory
name removal, this is valid as a user cannot insert an arbitrary
name to remove from the directory btree.

However, in the case of the attribute tree, a user has direct
control over the attribute name and can ask for any random name to
be removed without any validation. In this case, fsstress is asking
for a non-existent user.selinux attribute to be removed, and that is
causing xfs_da_path_shift() to fall off the bottom of the tree where
it asserts that a lookup failure is allowed. Because the flag is not
set, we die a horrible death on a debug enable kernel.

Prevent this assert from firing on attribute removes by adding the
op_flag XFS_DA_OP_OKNOENT to atribute removal operations.

Discovered when testing on a SELinux enabled system by fsstress in
test 070 by trying to remove a non-existent user.selinux attribute.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
This commit is contained in:
Dave Chinner 2011-06-23 01:35:01 +00:00 committed by Alex Elder
parent df4368a146
commit 4a33821236
1 changed files with 7 additions and 0 deletions
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7
fs/xfs/xfs_attr.c
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@ -489,6 +489,13 @@ xfs_attr_remove_int(xfs_inode_t *dp, struct xfs_name *name, int flags)
args.total = 0;
args.whichfork = XFS_ATTR_FORK;
/*
* we have no control over the attribute names that userspace passes us
* to remove, so we have to allow the name lookup prior to attribute
* removal to fail.
*/
args.op_flags = XFS_DA_OP_OKNOENT;
/*
* Attach the dquots to the inode.
*/