From: Yunseong Kim <yskelg(a)gmail.com>
mainline inclusion
from mainline-v6.13-rc1
commit 9a8c5d89d327ff58e9b2517f8a6afb4181d32c6e
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBEAF6
CVE: CVE-2024-53186
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?…
--------------------------------
A race condition exists between SMB request handling in
`ksmbd_conn_handler_loop()` and the freeing of `ksmbd_conn` in the
workqueue handler `handle_ksmbd_work()`. This leads to a UAF.
- KASAN: slab-use-after-free Read in handle_ksmbd_work
- KASAN: slab-use-after-free in rtlock_slowlock_locked
This race condition arises as follows:
- `ksmbd_conn_handler_loop()` waits for `conn->r_count` to reach zero:
`wait_event(conn->r_count_q, atomic_read(&conn->r_count) == 0);`
- Meanwhile, `handle_ksmbd_work()` decrements `conn->r_count` using
`atomic_dec_return(&conn->r_count)`, and if it reaches zero, calls
`ksmbd_conn_free()`, which frees `conn`.
- However, after `handle_ksmbd_work()` decrements `conn->r_count`,
it may still access `conn->r_count_q` in the following line:
`waitqueue_active(&conn->r_count_q)` or `wake_up(&conn->r_count_q)`
This results in a UAF, as `conn` has already been freed.
The discovery of this UAF can be referenced in the following PR for
syzkaller's support for SMB requests.
Link: https://github.com/google/syzkaller/pull/5524
Fixes: ee426bfb9d09 ("ksmbd: add refcnt to ksmbd_conn struct")
Cc: linux-cifs(a)vger.kernel.org
Cc: stable(a)vger.kernel.org # v6.6.55+, v6.10.14+, v6.11.3+
Cc: syzkaller(a)googlegroups.com
Signed-off-by: Yunseong Kim <yskelg(a)gmail.com>
Acked-by: Namjae Jeon <linkinjeon(a)kernel.org>
Signed-off-by: Steve French <stfrench(a)microsoft.com>
Signed-off-by: Yifan Qiao <qiaoyifan4(a)huawei.com>
---
fs/smb/server/server.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/smb/server/server.c b/fs/smb/server/server.c
index b6e0b71c281d..1450e007ac70 100644
--- a/fs/smb/server/server.c
+++ b/fs/smb/server/server.c
@@ -276,8 +276,12 @@ static void handle_ksmbd_work(struct work_struct *wk)
* disconnection. waitqueue_active is safe because it
* uses atomic operation for condition.
*/
+ atomic_inc(&conn->refcnt);
if (!atomic_dec_return(&conn->r_count) && waitqueue_active(&conn->r_count_q))
wake_up(&conn->r_count_q);
+
+ if (atomic_dec_and_test(&conn->refcnt))
+ kfree(conn);
}
/**
--
2.39.2