This is a note to let you know that I've just added the patch titled
xfs: make sure the rt allocator doesn't run off the end
to the 5.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xfs-make-sure-the-rt-allocator-doesn-t-run-off-the-e.patch
and it can be found in the queue-5.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 028a9cf564ab6aec26ead2dc2ced8c19baa6ba56
Author: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Date: Wed Sep 9 14:21:06 2020 -0700
xfs: make sure the rt allocator doesn't run off the end
[ Upstream commit 2a6ca4baed620303d414934aa1b7b0a8e7bab05f ]
There's an overflow bug in the realtime allocator. If the rt volume is
large enough to handle a single allocation request that is larger than
the maximum bmap extent length and the rt bitmap ends exactly on a
bitmap block boundary, it's possible that the near allocator will try to
check the freeness of a range that extends past the end of the bitmap.
This fails with a corruption error and shuts down the fs.
Therefore, constrain maxlen so that the range scan cannot run off the
end of the rt bitmap.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index 6209e7b6b895b..86994d7f7cba3 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -247,6 +247,9 @@ xfs_rtallocate_extent_block(
end = XFS_BLOCKTOBIT(mp, bbno + 1) - 1;
i <= end;
i++) {
+ /* Make sure we don't scan off the end of the rt volume. */
+ maxlen = min(mp->m_sb.sb_rextents, i + maxlen) - i;
+
/*
* See if there's a free extent of maxlen starting at i.
* If it's not so then next will contain the first non-free.
@@ -442,6 +445,14 @@ xfs_rtallocate_extent_near(
*/
if (bno >= mp->m_sb.sb_rextents)
bno = mp->m_sb.sb_rextents - 1;
+
+ /* Make sure we don't run off the end of the rt volume. */
+ maxlen = min(mp->m_sb.sb_rextents, bno + maxlen) - bno;
+ if (maxlen < minlen) {
+ *rtblock = NULLRTBLOCK;
+ return 0;
+ }
+
/*
* Try the exact allocation first.
*/
