On Thu, Oct 26, 2017 at 03:49:36PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Abort an dir/attr btree 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, which livelocks on
> the cycle in the attr btree.
>
> Apply the same checks to xfs_da3_node_lookup_int.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> fs/xfs/libxfs/xfs_da_btree.c | 22 +++++++++++++++++++++-
> fs/xfs/xfs_attr_list.c | 20 ++++++++++++++++++++
> 2 files changed, 41 insertions(+), 1 deletion(-)
>
>
> diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
> index 6d43358..6516115 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.c
> +++ b/fs/xfs/libxfs/xfs_da_btree.c
> @@ -1466,6 +1466,7 @@ xfs_da3_node_lookup_int(
> int max;
> int error;
> int retval;
> + unsigned int expected_level = 0;
> struct xfs_inode *dp = state->args->dp;
>
> args = state->args;
> @@ -1474,7 +1475,7 @@ xfs_da3_node_lookup_int(
> * Descend thru the B-tree searching each level for the right
> * node to use, until the right hashval is found.
> */
> - blkno = (args->whichfork == XFS_DATA_FORK)? args->geo->leafblk : 0;
> + blkno = args->geo->leafblk;
> for (blk = &state->path.blk[0], state->path.active = 1;
> state->path.active <= XFS_DA_NODE_MAXDEPTH;
> blk++, state->path.active++) {
> @@ -1517,6 +1518,18 @@ xfs_da3_node_lookup_int(
> dp->d_ops->node_hdr_from_disk(&nodehdr, node);
> btree = dp->d_ops->node_tree_p(node);
>
> + /* Tree taller than we can handle; bail out! */
> + if (nodehdr.level >= XFS_DA_NODE_MAXDEPTH)
> + return -EFSCORRUPTED;
> +
> + /* Check the level from the root. */
> + if (blkno == args->geo->leafblk)
> + expected_level = nodehdr.level - 1;
> + else if (expected_level != nodehdr.level)
> + return -EFSCORRUPTED;
> + else
> + expected_level--;
> +
> max = nodehdr.count;
> blk->hashval = be32_to_cpu(btree[max - 1].hashval);
>
> @@ -1562,8 +1575,15 @@ xfs_da3_node_lookup_int(
> blk->index = probe;
> blkno = be32_to_cpu(btree[probe].before);
> }
> +
> + /* We can't point back to the root. */
> + if (blkno == args->geo->leafblk)
> + return -EFSCORRUPTED;
> }
>
> + if (expected_level != 0)
> + return -EFSCORRUPTED;
> +
> /*
> * A leaf block that ends in the hashval that we are interested in
> * (final hashval == search hashval) means that the next block may
> diff --git a/fs/xfs/xfs_attr_list.c b/fs/xfs/xfs_attr_list.c
> index 021ec5a..a360310 100644
> --- a/fs/xfs/xfs_attr_list.c
> +++ b/fs/xfs/xfs_attr_list.c
> @@ -223,6 +223,7 @@ xfs_attr_node_list_lookup(
> struct xfs_buf *bp;
> int i;
> int error = 0;
> + unsigned int expected_level = 0;
> uint16_t magic;
>
> ASSERT(*pbp == NULL);
> @@ -246,6 +247,18 @@ xfs_attr_node_list_lookup(
>
> dp->d_ops->node_hdr_from_disk(&nodehdr, node);
>
> + /* Tree taller than we can handle; bail out! */
> + if (nodehdr.level >= XFS_DA_NODE_MAXDEPTH)
> + goto out_corruptbuf;
> +
> + /* Check the level from the root node. */
> + if (cursor->blkno == 0)
> + expected_level = nodehdr.level - 1;
> + else if (expected_level != nodehdr.level)
> + goto out_corruptbuf;
> + else
> + expected_level--;
> +
> btree = dp->d_ops->node_tree_p(node);
> for (i = 0; i < nodehdr.count; btree++, i++) {
> if (cursor->hashval <= be32_to_cpu(btree->hashval)) {
> @@ -259,8 +272,15 @@ xfs_attr_node_list_lookup(
>
> if (i == nodehdr.count)
> return 0;
> +
> + /* We can't point back to the root. */
> + if (cursor->blkno == 0)
> + return -EFSCORRUPTED;
> }
>
> + if (expected_level != 0)
> + goto out_corruptbuf;
> +
> *pbp = bp;
> return 0;
>
>
> --
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