From 2a6ca4baed620303d414934aa1b7b0a8e7bab05f Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Wed, 9 Sep 2020 14:21:06 -0700 Subject: [PATCH] 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 Reviewed-by: Christoph Hellwig --- fs/xfs/xfs_rtalloc.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c index 0558f92ecdb8..5b89c12f1566 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. */