[PATCH 3.16 031/245] Btrfs: fix BUG_ON in btrfs_mark_buffer_dirty

Ben Hutchings
2020-04-23T23:24:25Z

From: Liu Bo <bo.li.liu@oracle.com>

commit ef85b25e982b5bba1530b936e283ef129f02ab9d upstream.

This can only happen with CONFIG_BTRFS_FS_CHECK_INTEGRITY=y.

Commit 1ba98d0 ("Btrfs: detect corruption when non-root leaf has zero item")
assumes that a leaf is its root when leaf->bytenr == btrfs_root_bytenr(root),
however, we should not use btrfs_root_bytenr(root) since it's mainly got
updated during committing transaction. So the check can fail when doing
COW on this leaf while it is a root.

This changes to use "if (leaf == btrfs_root_node(root))" instead, just like
how we check whether leaf is a root in __btrfs_cow_block().

Fixes: 1ba98d086fe3 (Btrfs: detect corruption when non-root leaf has zero item)
Reported-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/btrfs/disk-io.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -533,13 +533,17 @@ static noinline int check_leaf(struct bt
* open_ctree() some roots has not yet been set up.
*/
if (!IS_ERR_OR_NULL(check_root)) {
+ struct extent_buffer *eb;
+
+ eb = btrfs_root_node(check_root);
/* if leaf is the root, then it's fine */
- if (leaf->start !=
- btrfs_root_bytenr(&check_root->root_item)) {
+ if (leaf != eb) {
CORRUPT("non-root leaf's nritems is 0",
- leaf, root, 0);
+ leaf, check_root, 0);
+ free_extent_buffer(eb);
return -EIO;
}
+ free_extent_buffer(eb);
}
return 0;
}