[PATCH] btrfs: add a sanity check for btrfs root

From: Lizhi Xu
Date: Fri Oct 25 2024 - 00:56:12 EST


Syzbot report a null-ptr-deref in btrfs_search_slot.
It use the input logical can't find the extent root in extent_from_logical,
and triger the null-ptr-deref in btrfs_search_slot.
Add sanity check for btrfs root before using it in btrfs_search_slot.

Reported-by: syzbot+3030e17bd57a73d39bd7@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=3030e17bd57a73d39bd7
Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
---
fs/btrfs/ctree.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 0cc919d15b14..9c05cab473f5 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2010,7 +2010,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root,
const struct btrfs_key *key, struct btrfs_path *p,
int ins_len, int cow)
{
- struct btrfs_fs_info *fs_info = root->fs_info;
+ struct btrfs_fs_info *fs_info;
struct extent_buffer *b;
int slot;
int ret;
@@ -2023,6 +2023,10 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root,
int min_write_lock_level;
int prev_cmp;

+ if (!root)
+ return -EINVAL;
+
+ fs_info = root->fs_info;
might_sleep();

lowest_level = p->lowest_level;
--
2.43.0