[PATCH] btrfs: qgroup: fix slab-out-of-bounds in btrfs_qgroup_inherit

[Jeongjun Park <aha310510@gmail.com>]

If a value exists in inherit->num_ref_copies or inherit->num_excl_copies,
an out-of-bounds vulnerability occurs.

Therefore, you need to add code to check the presence or absence of 
that value.

Regards.
Jeongjun Park.

Reported-by: syzbot+a0d1f7e26910be4dc171@syzkaller.appspotmail.com
Fixes: 3f5e2d3b3877 ("Btrfs: fix missing check in the btrfs_qgroup_inherit()")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
 fs/btrfs/qgroup.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/qgroup.c b /fs/btrfs/qgroup.c
index fc2a7ea26354..23beac746637 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -3270,6 +3270,10 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
 	}
 
 	if (inherit) {
+		if (inherit->num_ref_copies > 0 || inherit->num_excl_copies > 0) {
+			ret = -EINVAL;
+			goto out;
+		}
 		i_qgroups = (u64 *)(inherit + 1);
 		nums = inherit->num_qgroups + 2 * inherit->num_ref_copies +
 		       2 * inherit->num_excl_copies;
--