CVE-2024-56640

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

net/smc: fix LGR and link use-after-free issue

We encountered a LGR/link use-after-free issue, which manifested as

the LGR/link refcnt reaching 0 early and entering the clear process,

making resource access unsafe.

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

WARNING: CPU: 14 PID: 107447 at lib/refcount.c:25 refcount_warn_saturate+0x9c/0x140

Workqueue: events smc_lgr_terminate_work [smc]

Call trace:

refcount_warn_saturate+0x9c/0x140

__smc_lgr_terminate.part.45+0x2a8/0x370 [smc]

smc_lgr_terminate_work+0x28/0x30 [smc]

process_one_work+0x1b8/0x420

worker_thread+0x158/0x510

kthread+0x114/0x118

or

refcount_t: underflow; use-after-free.

WARNING: CPU: 6 PID: 93140 at lib/refcount.c:28 refcount_warn_saturate+0xf0/0x140

Workqueue: smc_hs_wq smc_listen_work [smc]

Call trace:

refcount_warn_saturate+0xf0/0x140

smcr_link_put+0x1cc/0x1d8 [smc]

smc_conn_free+0x110/0x1b0 [smc]

smc_conn_abort+0x50/0x60 [smc]

smc_listen_find_device+0x75c/0x790 [smc]

smc_listen_work+0x368/0x8a0 [smc]

process_one_work+0x1b8/0x420

worker_thread+0x158/0x510

kthread+0x114/0x118

It is caused by repeated release of LGR/link refcnt. One suspect is that

smc_conn_free() is called repeatedly because some smc_conn_free() from

server listening path are not protected by sock lock.

e.g.

Calls under socklock | smc_listen_work

-------------------------------------------------------

lock_sock(sk) | smc_conn_abort

smc_conn_free | \- smc_conn_free

\- smcr_link_put | \- smcr_link_put (duplicated)

release_sock(sk)

So here add sock lock protection in smc_listen_work() path, making it

exclusive with other connection operations.