diff mbox series

[v5,30/52] btrfs: validate ->reloc_root after recording root in trans

Message ID bbadccc46005510ced7ce5a7fbe667b03340b688.1607349282.git.josef@toxicpanda.com (mailing list archive)
State New, archived
Headers show
Series Cleanup error handling in relocation | expand

Commit Message

Josef Bacik Dec. 7, 2020, 1:57 p.m. UTC 
If we fail to setup a ->reloc_root in a different thread that path will
error out, however it still leaves root->reloc_root NULL but would still
appear set up in the transaction.  Subsequent calls to
btrfs_record_root_in_transaction would succeed without attempting to
create the reloc root, as the transid has already been update.  Handle
this case by making sure we have a root->reloc_root set after a
btrfs_record_root_in_transaction call so we don't end up deref'ing a
NULL pointer.

Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/relocation.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
diff mbox series

Patch

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 627c1bcfdd33..5770f4212772 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2073,6 +2073,13 @@  struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
 			return ERR_PTR(ret);
 		root = root->reloc_root;
 
+		/*
+		 * We could have raced with another thread which failed, so
+		 * ->reloc_root may not be set, return -ENOENT in this case.
+		 */
+		if (!root)
+			return ERR_PTR(-ENOENT);
+
 		if (next->new_bytenr != root->node->start) {
 			/*
 			 * We just created the reloc root, so we shouldn't have
@@ -2572,6 +2579,14 @@  static int relocate_tree_block(struct btrfs_trans_handle *trans,
 			ret = btrfs_record_root_in_trans(trans, root);
 			if (ret)
 				goto out;
+			/*
+			 * Another thread could have failed, need to check if we
+			 * have ->reloc_root actually set.
+			 */
+			if (!root->reloc_root) {
+				ret = -ENOENT;
+				goto out;
+			}
 			root = root->reloc_root;
 			node->new_bytenr = root->node->start;
 			btrfs_put_root(node->root);