CVE-2023-53445

In the Linux kernel, the following vulnerability has been resolved:

net: qrtr: Fix a refcount bug in qrtr_recvmsg()

Syzbot reported a bug as following:

refcount_t: addition on 0; use-after-free.

...

RIP: 0010:refcount_warn_saturate+0x17c/0x1f0 lib/refcount.c:25

...

Call Trace:

<TASK>

__refcount_add include/linux/refcount.h:199 [inline]

__refcount_inc include/linux/refcount.h:250 [inline]

refcount_inc include/linux/refcount.h:267 [inline]

kref_get include/linux/kref.h:45 [inline]

qrtr_node_acquire net/qrtr/af_qrtr.c:202 [inline]

qrtr_node_lookup net/qrtr/af_qrtr.c:398 [inline]

qrtr_send_resume_tx net/qrtr/af_qrtr.c:1003 [inline]

qrtr_recvmsg+0x85f/0x990 net/qrtr/af_qrtr.c:1070

sock_recvmsg_nosec net/socket.c:1017 [inline]

sock_recvmsg+0xe2/0x160 net/socket.c:1038

qrtr_ns_worker+0x170/0x1700 net/qrtr/ns.c:688

process_one_work+0x991/0x15c0 kernel/workqueue.c:2390

worker_thread+0x669/0x1090 kernel/workqueue.c:2537

It occurs in the concurrent scenario of qrtr_recvmsg() and

qrtr_endpoint_unregister() as following:

cpu0 cpu1

qrtr_recvmsg qrtr_endpoint_unregister

qrtr_send_resume_tx qrtr_node_release

qrtr_node_lookup mutex_lock(&qrtr_node_lock)

spin_lock_irqsave(&qrtr_nodes_lock, ) refcount_dec_and_test(&node->ref) [node->ref == 0]

radix_tree_lookup [node != NULL] __qrtr_node_release

qrtr_node_acquire spin_lock_irqsave(&qrtr_nodes_lock, )

kref_get(&node->ref) [WARNING] ...

mutex_unlock(&qrtr_node_lock)

Use qrtr_node_lock to protect qrtr_node_lookup() implementation, this

is actually improving the protection of node reference.