This is a note to let you know that I've just added the patch titled

xfs: fix log block underflow during recovery cycle verification

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: xfs-fix-log-block-underflow-during-recovery-cycle-verification.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Mon Dec 18 14:12:35 CET 2017

From: Brian Foster bfoster@redhat.com Date: Thu, 26 Oct 2017 09:31:16 -0700 Subject: xfs: fix log block underflow during recovery cycle verification

From: Brian Foster bfoster@redhat.com

[ Upstream commit 9f2a4505800607e537e9dd9dea4f55c4b0c30c7a ]

It is possible for mkfs to format very small filesystems with too small of an internal log with respect to the various minimum size and block count requirements. If this occurs when the log happens to be smaller than the scan window used for cycle verification and the scan wraps the end of the log, the start_blk calculation in xlog_find_head() underflows and leads to an attempt to scan an invalid range of log blocks. This results in log recovery failure and a failed mount.

Since there may be filesystems out in the wild with this kind of geometry, we cannot simply refuse to mount. Instead, cap the scan window for cycle verification to the size of the physical log. This ensures that the cycle verification proceeds as expected when the scan wraps the end of the log.

Reported-by: Zorro Lang zlang@redhat.com 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: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/xfs/xfs_log_recover.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/xfs/xfs_log_recover.c +++ b/fs/xfs/xfs_log_recover.c @@ -753,7 +753,7 @@ xlog_find_head( * in the in-core log. The following number can be made tighter if * we actually look at the block size of the filesystem. */ - num_scan_bblks = XLOG_TOTAL_REC_SHIFT(log); + num_scan_bblks = min_t(int, log_bbnum, XLOG_TOTAL_REC_SHIFT(log)); if (head_blk >= num_scan_bblks) { /* * We are guaranteed that the entire check can be performed

Patches currently in stable-queue which might be from bfoster@redhat.com are

queue-4.9/xfs-fix-incorrect-extent-state-in-xfs_bmap_add_extent_unwritten_real.patch queue-4.9/xfs-fix-log-block-underflow-during-recovery-cycle-verification.patch queue-4.9/xfs-truncate-pagecache-before-writeback-in-xfs_setattr_size.patch