[PATCH] xfs: fix quotacheck dquot id overflow infinite loop

[Brian Foster <bfoster@redhat.com>]

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>
---
 fs/xfs/xfs_qm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index 6ce948c..15751dc 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -111,6 +111,9 @@ xfs_qm_dquot_walk(
 			skipped = 0;
 			break;
 		}
+		/* we're done if id overflows back to zero */
+		if (!next_index)
+			break;
 	}
 
 	if (skipped) {
-- 
2.9.4