Commit 2a6ca4ba authored Sep 09, 2020 by Darrick J. Wong

xfs: make sure the rt allocator doesn't run off the end



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@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

parent 0f4ec0f1

fs/xfs/xfs_rtalloc.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -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.
		*/

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