@@ -1900,6 +1900,7 @@ static void smc_listen_out(struct smc_sock *new_smc)
if (tcp_sk(new_smc->clcsock->sk)->syn_smc)
atomic_dec(&lsmc->queued_smc_hs);
+ release_sock(newsmcsk); /* lock in smc_listen_work() */
if (lsmc->sk.sk_state == SMC_LISTEN) {
lock_sock_nested(&lsmc->sk, SINGLE_DEPTH_NESTING);
smc_accept_enqueue(&lsmc->sk, newsmcsk);
@@ -2421,6 +2422,7 @@ static void smc_listen_work(struct work_struct *work)
u8 accept_version;
int rc = 0;
+ lock_sock(&new_smc->sk); /* release in smc_listen_out() */
if (new_smc->listen_smc->sk.sk_state != SMC_LISTEN)
return smc_listen_out_err(new_smc);
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. Fixes: 3b2dec2603d5 ("net/smc: restructure client and server code in af_smc") Co-developed-by: Guangguan Wang <guangguan.wang@linux.alibaba.com> Signed-off-by: Guangguan Wang <guangguan.wang@linux.alibaba.com> Co-developed-by: Kai <KaiShen@linux.alibaba.com> Signed-off-by: Kai <KaiShen@linux.alibaba.com> Signed-off-by: Wen Gu <guwen@linux.alibaba.com> --- net/smc/af_smc.c | 2 ++ 1 file changed, 2 insertions(+)