xfs: don't ever return a stale pointer from __xfs_dir3_free_read

[ Upstream commit 1cb5deb5bc095c070c09a4540c45f9c9ba24be43 ]

If we decide that a directory free block is corrupt, we must take care
not to leak a buffer pointer to the caller.  After xfs_trans_brelse
returns, the buffer can be freed or reused, which means that we have to
set *bpp back to NULL.

Callers are supposed to notice the nonzero return value and not use the
buffer pointer, but we should code more defensively, even if all current
callers handle this situation correctly.

Fixes: de14c5f541e7 ("xfs: verify free block header fields")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/xfs/libxfs/xfs_dir2_node.c b/fs/xfs/libxfs/xfs_dir2_node.c
index 682e2bf370c72923b43ee7da7d778ba774f66551..ee4ebc2dd749257a96e7f86351b4c36624e28f0c 100644 (file)
--- a/fs/xfs/libxfs/xfs_dir2_node.c
+++ b/fs/xfs/libxfs/xfs_dir2_node.c
@@ -212,6 +212,7 @@ __xfs_dir3_free_read(
                xfs_buf_ioerror(*bpp, -EFSCORRUPTED);
                xfs_verifier_error(*bpp);
                xfs_trans_brelse(tp, *bpp);
+               *bpp = NULL;
                return -EFSCORRUPTED;
        }