linux-kernel - [PATCH 4.9 44/78] xfs: fix quotacheck dquot id overflow infinite loop

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Message-Id: <20170918091132.950894043@linuxfoundation.org>
Date:   Mon, 18 Sep 2017 11:11:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Brian Foster <bfoster@...hat.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>
Subject: [PATCH 4.9 44/78] xfs: fix quotacheck dquot id overflow infinite loop

4.9-stable review patch.  If anyone has any objections, please let me know.

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


From: Brian Foster <bfoster@...hat.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@...hat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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) {