6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Wen Gu guwen@linux.alibaba.com
[ Upstream commit 2c7f14ed9c19ec0f149479d1c2842ec1f9bf76d7 ]
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 Reviewed-by: Wenjia Zhang wenjia@linux.ibm.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/smc/af_smc.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index ed6d4d520bc7a..9e6c69d18581c 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -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);