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Commit d2a047f3 authored by Darrick J. Wong's avatar Darrick J. Wong Committed by Dave Chinner
Browse files

xfs: forbid AG btrees with level == 0 



There is no such thing as a zero-level AG btree since even a single-node
zero-records btree has one level.  Btree cursor constructors read
cur_nlevels straight from disk and then access things like
cur_bufs[cur_nlevels - 1] which is /really/ bad if cur_nlevels is zero!
Therefore, strengthen the verifiers to prevent this possibility.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent f7a136ae

fs/xfs/libxfs/xfs_alloc.c

+7 −3
Original line number Diff line number Diff line
@@ -2455,12 +2455,15 @@ xfs_agf_verify( 
	      be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp)))

		return false;



	if (be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]) > XFS_BTREE_MAXLEVELS ||

	if (be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]) < 1 ||

	    be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]) < 1 ||

	    be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]) > XFS_BTREE_MAXLEVELS ||

	    be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]) > XFS_BTREE_MAXLEVELS)

		return false;



	if (xfs_sb_version_hasrmapbt(&mp->m_sb) &&

	    be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]) > XFS_BTREE_MAXLEVELS)

	    (be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]) < 1 ||

	     be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]) > XFS_BTREE_MAXLEVELS))

		return false;



	/*
@@ -2477,7 +2480,8 @@ xfs_agf_verify( 
		return false;



	if (xfs_sb_version_hasreflink(&mp->m_sb) &&

	    be32_to_cpu(agf->agf_refcount_level) > XFS_BTREE_MAXLEVELS)

	    (be32_to_cpu(agf->agf_refcount_level) < 1 ||

	     be32_to_cpu(agf->agf_refcount_level) > XFS_BTREE_MAXLEVELS))

		return false;



	return true;;

fs/xfs/libxfs/xfs_ialloc.c

+8 −1
Original line number Diff line number Diff line
@@ -2510,8 +2510,15 @@ xfs_agi_verify( 
	if (!XFS_AGI_GOOD_VERSION(be32_to_cpu(agi->agi_versionnum)))

		return false;



	if (be32_to_cpu(agi->agi_level) > XFS_BTREE_MAXLEVELS)

	if (be32_to_cpu(agi->agi_level) < 1 ||

	    be32_to_cpu(agi->agi_level) > XFS_BTREE_MAXLEVELS)

		return false;



	if (xfs_sb_version_hasfinobt(&mp->m_sb) &&

	    (be32_to_cpu(agi->agi_free_level) < 1 ||

	     be32_to_cpu(agi->agi_free_level) > XFS_BTREE_MAXLEVELS))

		return false;



	/*

	 * during growfs operations, the perag is not fully initialised,

	 * so we can't use it for any useful checking. growfs ensures we can't