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Subject[PATCH 4.9 44/78] xfs: fix quotacheck dquot id overflow infinite loop
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------


From: Brian Foster <bfoster@redhat.com>

commit cfaf2d034360166e569a4929dd83ae9698bed856 upstream.

If a dquot has an id of U32_MAX, the next lookup index increment
overflows the uint32_t back to 0. This starts the lookup sequence
over from the beginning, repeats indefinitely and results in a
livelock.

Update xfs_qm_dquot_walk() to explicitly check for the lookup
overflow and exit the loop.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/xfs/xfs_qm.c | 3 +++
1 file changed, 3 insertions(+)

--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -111,6 +111,9 @@ restart:
skipped = 0;
break;
}
+ /* we're done if id overflows back to zero */
+ if (!next_index)
+ break;
}

if (skipped) {

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