Commit 4d09807f authored Apr 12, 2019 by Brian Foster Committed by Darrick J. Wong Apr 14, 2019

xfs: fix use after free in buf log item unlock assert

The xfs_buf_log_item ->iop_unlock() callback asserts that the buffer
is unlocked when either non-stale or aborted. This assert occurs
after the bli refcount has been dropped and the log item potentially
freed. The aborted check is thus a potential use after free. This
problem has been reproduced with KASAN enabled via generic/475.

Fix up xfs_buf_item_unlock() to query aborted state before the bli
reference is dropped to prevent a potential use after free.

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>

parent dc4060a5

fs/xfs/xfs_buf_item.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -605,6 +605,8 @@ xfs_buf_item_unlock(
		#if defined(DEBUG) \|\| defined(XFS_WARN)
		bool ordered = bip->bli_flags & XFS_BLI_ORDERED;
		bool dirty = bip->bli_flags & XFS_BLI_DIRTY;
		bool aborted = test_bit(XFS_LI_ABORTED,
		&lip->li_flags);
		#endif

		trace_xfs_buf_item_unlock(bip);
		@@ -633,7 +635,7 @@ xfs_buf_item_unlock(
		released = xfs_buf_item_put(bip);
		if (hold \|\| (stale && !released))
		return;
		ASSERT(!stale \|\| test_bit(XFS_LI_ABORTED, &lip->li_flags));
		ASSERT(!stale \|\| aborted);
		xfs_buf_relse(bp);
		}

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