[PATCH 2/4] xfs: abort dir/attr btree operation if btree is obviously weird

Darrick J. Wong
2017-10-26T05:49:33Z

From: Darrick J. Wong <darrick.wong@oracle.com>

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@oracle.com>
---
fs/xfs/libxfs/xfs_da_btree.c | 34 +++++++++++++++++++++++++++++++++-
fs/xfs/xfs_attr_list.c | 32 ++++++++++++++++++++++++++++++++
2 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
index 6d43358..3dbeda6 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 = -1U;
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++) {
@@ -1496,6 +1497,8 @@ xfs_da3_node_lookup_int(
blk->magic == XFS_ATTR3_LEAF_MAGIC) {
blk->magic = XFS_ATTR_LEAF_MAGIC;
blk->hashval = xfs_attr_leaf_lasthash(blk->bp, NULL);
+ if (expected_level == -1U)
+ expected_level = 0;
break;
}

@@ -1504,6 +1507,8 @@ xfs_da3_node_lookup_int(
blk->magic = XFS_DIR2_LEAFN_MAGIC;
blk->hashval = xfs_dir2_leaf_lasthash(args->dp,
blk->bp, NULL);
+ if (expected_level == -1U)
+ expected_level = 0;
break;
}

@@ -1517,6 +1522,26 @@ 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;
+
+ if (blkno == args->geo->leafblk) {
+ /*
+ * 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.
+ */
+ return -EFSCORRUPTED;
+ } else {
+ expected_level--;
+ }
+
max = nodehdr.count;
blk->hashval = be32_to_cpu(btree[max - 1].hashval);

@@ -1562,8 +1587,15 @@ 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 48423eb..9a8dafc 100644
--- a/fs/xfs/xfs_attr_list.c
+++ b/fs/xfs/xfs_attr_list.c
@@ -222,6 +222,7 @@ xfs_attr_node_list_lookup(
struct xfs_trans *tp = context->tp;
int i;
int error = 0;
+ unsigned int expected_level = -1U;
uint16_t magic;

ASSERT(*pbp == NULL);
@@ -236,6 +237,8 @@ xfs_attr_node_list_lookup(
switch (magic) {
case XFS_ATTR_LEAF_MAGIC:
case XFS_ATTR3_LEAF_MAGIC:
+ if (expected_level == -1U)
+ expected_level = 0;
goto found_leaf;
case XFS_DA_NODE_MAGIC:
case XFS_DA3_NODE_MAGIC:
@@ -249,6 +252,26 @@ 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;
+
+ 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.
+ */
+ 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)) {
@@ -262,15 +285,24 @@ xfs_attr_node_list_lookup(
goto out_buf;

xfs_trans_brelse(tp, *pbp);
+
+ /* We can't point back to the root. */
+ if (cursor->blkno == 0) {
+ error = -EFSCORRUPTED;
+ goto out;
+ }
}

found_leaf:
+ if (expected_level != 0)
+ goto out_corruptbuf;
return error;

out_corruptbuf:
error = -EFSCORRUPTED;
out_buf:
xfs_trans_brelse(tp, *pbp);
+out:
*pbp = NULL;
return error;
}