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

From: Qu Wenruo
Date: Mon Jun 24 2024 - 01:10:52 EST




在 2024/6/24 12:37, Jeongjun Park 写道:
If a value exists in inherit->num_ref_copies or inherit->num_excl_copies,
an out-of-bounds vulnerability occurs.


Thanks for the fix.

Although I'm still not 100% sure what's going wrong.

The original report
(https://lore.kernel.org/lkml/000000000000bc19ba061a67ca77@xxxxxxxxxx/T/)
is showing a backtrace when creating snapshot.

In that case they should all go through __btrfs_ioctl_snap_create(), and
since it has qgroup_inherit, it can only come from
btrfs_ioctl_snap_create_v2().

But in that function, we have just called btrfs_qgroup_check_inherit()
function and it already has the check on num_ref_copies/num_excl_copies.

So in that case it should not even happen.

I think the root cause is why the existing btrfs_qgroup_check_inherit()
doesn't catch the problem in the first place.

Thanks,
Qu

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

Regards.
Jeongjun Park.

Reported-by: syzbot+a0d1f7e26910be4dc171@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 3f5e2d3b3877 ("Btrfs: fix missing check in the btrfs_qgroup_inherit()")
Signed-off-by: Jeongjun Park <aha310510@xxxxxxxxx>
---
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;
--