CVE-2022-50555

Summary

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

tipc: fix a null-ptr-deref in tipc_topsrv_accept

syzbot found a crash in tipc_topsrv_accept:

KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] Workqueue: tipc_rcv tipc_topsrv_accept RIP: 0010:kernel_accept+0x22d/0x350 net/socket.c:3487 Call Trace: <TASK> tipc_topsrv_accept+0x197/0x280 net/tipc/topsrv.c:460 process_one_work+0x991/0x1610 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e4/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

It was caused by srv->listener that might be set to null by tipc_topsrv_stop() in net .exit whereas it's still used in tipc_topsrv_accept() worker.

srv->listener is protected by srv->idr_lock in tipc_topsrv_stop(), so add a check for srv->listener under srv->idr_lock in tipc_topsrv_accept() to avoid the null-ptr-deref. To ensure the lsock is not released during the tipc_topsrv_accept(), move sock_release() after tipc_topsrv_work_stop() where it's waiting until the tipc_topsrv_accept worker to be done.

Note that sk_callback_lock is used to protect sk->sk_user_data instead of srv->listener, and it should check srv in tipc_topsrv_listener_data_ready() instead. This also ensures that no more tipc_topsrv_accept worker will be started after tipc_conn_close() is called in tipc_topsrv_stop() where it sets sk->sk_user_data to null.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/ce69bdac2310152bb70845024d5d704c52aabfc3
• https://git.kernel.org/stable/c/24b129aed8730e48f47d852d58d76825ab6f407c
• https://git.kernel.org/stable/c/32a3d4660b34ce49ac0162338ebe362098e2f5df
• https://git.kernel.org/stable/c/7a939503fc32bff4ed60800b73ff7fbb4aea2142
• https://git.kernel.org/stable/c/cedb41664e27b2cae7e21487f1bee22dcd84037d
• https://git.kernel.org/stable/c/82cb4e4612c633a9ce320e1773114875604a3cce

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