On Mon, Oct 23, 2017 at 05:28:24PM -0700, Darrick J. Wong wrote:
> Abort an attribute list operation if the attr btree has obvious problems
> like loops back to the root or pointers don't point down the tree.
> Found by fuzzing btree[0].before to zero in xfs/402.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/xfs_attr_list.c | 54 ++++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 43 insertions(+), 11 deletions(-)
>
> diff --git a/fs/xfs/xfs_attr_list.c b/fs/xfs/xfs_attr_list.c
> index 5816786..9f6fcc6 100644
> --- a/fs/xfs/xfs_attr_list.c
> +++ b/fs/xfs/xfs_attr_list.c
...
> @@ -302,6 +306,30 @@ xfs_attr_node_list(xfs_attr_list_context_t *context)
> }
>
> dp->d_ops->node_hdr_from_disk(&nodehdr, node);
> +
> + /* Tree taller than we can handle; bail out! */
> + if (nodehdr.level >= XFS_DA_NODE_MAXDEPTH) {
> + xfs_trans_brelse(context->tp, bp);
> + return -EFSCORRUPTED;
> + }
> +
> + if (cursor->blkno == 0) {
> + /*
> + * This is the root node, set up for the
> + * next level we want to see.
> + */
> + expected_level = nodehdr.level - 1;
> + } else if (expected_level != nodehdr.level) {
> + /*
> + * Not the level we were expecting, which
> + * implies that the tree is bad.
> + */
> + xfs_trans_brelse(context->tp, bp);
> + return -EFSCORRUPTED;
> + } else {
> + expected_level--;
> + }
> +
It looks like we wouldn't catch the case of a two level tree having a
bad level, since we'd break out on leaf magic check above. Perhaps we
should check or assert that expected_level reaches 0? Otherwise looks Ok
to me.
Brian
> btree = dp->d_ops->node_tree_p(node);
> for (i = 0; i < nodehdr.count; btree++, i++) {
> if (cursor->hashval
> @@ -317,6 +345,10 @@ xfs_attr_node_list(xfs_attr_list_context_t *context)
> return 0;
> }
> xfs_trans_brelse(context->tp, bp);
> +
> + /* We can't point back to the root. */
> + if (cursor->blkno == 0)
> + return -EFSCORRUPTED;
> }
> }
> ASSERT(bp != NULL);
> --
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