6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
[ Upstream commit 3ed51857a50f530ac7a1482e069dfbd1298558d4 ]
Syzbot reports a null-ptr-deref in btrfs_search_slot().
The reproducer is using rescue=ibadroots, and the extent tree root is
corrupted thus the extent tree is NULL.
When scrub tries to search the extent tree to gather the needed extent
info, btrfs_search_slot() doesn't check if the target root is NULL or
not, resulting the null-ptr-deref.
Add sanity check for btrfs root before using it in btrfs_search_slot().
Reported-by: syzbot+3030e17bd57a73d39bd7@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 42437a6386ff ("btrfs: introduce mount option rescue=ignorebadroots")
Link: https://syzkaller.appspot.com/bug?extid=3030e17bd57a73d39bd7
CC: stable@xxxxxxxxxxxxxxx # 5.15+
Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
Tested-by: syzbot+3030e17bd57a73d39bd7@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 0cc919d15b144..9c05cab473f57 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
