From: Wen Gu guwen@linux.alibaba.com
[ Upstream commit c0bf3d8a943b6f2e912b7c1de03e2ef28e76f760 ]
We encountered a crash in smc_setsockopt() and it is caused by accessing smc->clcsock after clcsock was released.
BUG: kernel NULL pointer dereference, address: 0000000000000020 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 1 PID: 50309 Comm: nginx Kdump: loaded Tainted: G E 5.16.0-rc4+ #53 RIP: 0010:smc_setsockopt+0x59/0x280 [smc] Call Trace: <TASK> __sys_setsockopt+0xfc/0x190 __x64_sys_setsockopt+0x20/0x30 do_syscall_64+0x34/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f16ba83918e </TASK>
This patch tries to fix it by holding clcsock_release_lock and checking whether clcsock has already been released before access.
In case that a crash of the same reason happens in smc_getsockopt() or smc_switch_to_fallback(), this patch also checkes smc->clcsock in them too. And the caller of smc_switch_to_fallback() will identify whether fallback succeeds according to the return value.
Fixes: fd57770dd198 ("net/smc: wait for pending work before clcsock release_sock") Link: https://lore.kernel.org/lkml/5dd7ffd1-28e2-24cc-9442-1defec27375e@linux.ibm.... Signed-off-by: Wen Gu guwen@linux.alibaba.com Acked-by: Karsten Graul kgraul@linux.ibm.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/smc/af_smc.c | 63 +++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 51 insertions(+), 12 deletions(-)
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 211cd91b6c408..85e077a69c67d 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -566,12 +566,17 @@ static void smc_stat_fallback(struct smc_sock *smc) mutex_unlock(&net->smc.mutex_fback_rsn); }
-static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code) +static int smc_switch_to_fallback(struct smc_sock *smc, int reason_code) { wait_queue_head_t *smc_wait = sk_sleep(&smc->sk); - wait_queue_head_t *clc_wait = sk_sleep(smc->clcsock->sk); + wait_queue_head_t *clc_wait; unsigned long flags;
+ mutex_lock(&smc->clcsock_release_lock); + if (!smc->clcsock) { + mutex_unlock(&smc->clcsock_release_lock); + return -EBADF; + } smc->use_fallback = true; smc->fallback_rsn = reason_code; smc_stat_fallback(smc); @@ -586,18 +591,30 @@ static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code) * smc socket->wq, which should be removed * to clcsocket->wq during the fallback. */ + clc_wait = sk_sleep(smc->clcsock->sk); spin_lock_irqsave(&smc_wait->lock, flags); spin_lock_nested(&clc_wait->lock, SINGLE_DEPTH_NESTING); list_splice_init(&smc_wait->head, &clc_wait->head); spin_unlock(&clc_wait->lock); spin_unlock_irqrestore(&smc_wait->lock, flags); } + mutex_unlock(&smc->clcsock_release_lock); + return 0; }
/* fall back during connect */ static int smc_connect_fallback(struct smc_sock *smc, int reason_code) { - smc_switch_to_fallback(smc, reason_code); + struct net *net = sock_net(&smc->sk); + int rc = 0; + + rc = smc_switch_to_fallback(smc, reason_code); + if (rc) { /* fallback fails */ + this_cpu_inc(net->smc.smc_stats->clnt_hshake_err_cnt); + if (smc->sk.sk_state == SMC_INIT) + sock_put(&smc->sk); /* passive closing */ + return rc; + } smc_copy_sock_settings_to_clc(smc); smc->connect_nonblock = 0; if (smc->sk.sk_state == SMC_INIT) @@ -1514,11 +1531,12 @@ static void smc_listen_decline(struct smc_sock *new_smc, int reason_code, { /* RDMA setup failed, switch back to TCP */ smc_conn_abort(new_smc, local_first); - if (reason_code < 0) { /* error, no fallback possible */ + if (reason_code < 0 || + smc_switch_to_fallback(new_smc, reason_code)) { + /* error, no fallback possible */ smc_listen_out_err(new_smc); return; } - smc_switch_to_fallback(new_smc, reason_code); if (reason_code && reason_code != SMC_CLC_DECL_PEERDECL) { if (smc_clc_send_decline(new_smc, reason_code, version) < 0) { smc_listen_out_err(new_smc); @@ -1960,8 +1978,11 @@ static void smc_listen_work(struct work_struct *work)
/* check if peer is smc capable */ if (!tcp_sk(newclcsock->sk)->syn_smc) { - smc_switch_to_fallback(new_smc, SMC_CLC_DECL_PEERNOSMC); - smc_listen_out_connected(new_smc); + rc = smc_switch_to_fallback(new_smc, SMC_CLC_DECL_PEERNOSMC); + if (rc) + smc_listen_out_err(new_smc); + else + smc_listen_out_connected(new_smc); return; }
@@ -2250,7 +2271,9 @@ static int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
if (msg->msg_flags & MSG_FASTOPEN) { if (sk->sk_state == SMC_INIT && !smc->connect_nonblock) { - smc_switch_to_fallback(smc, SMC_CLC_DECL_OPTUNSUPP); + rc = smc_switch_to_fallback(smc, SMC_CLC_DECL_OPTUNSUPP); + if (rc) + goto out; } else { rc = -EINVAL; goto out; @@ -2443,6 +2466,11 @@ static int smc_setsockopt(struct socket *sock, int level, int optname, /* generic setsockopts reaching us here always apply to the * CLC socket */ + mutex_lock(&smc->clcsock_release_lock); + if (!smc->clcsock) { + mutex_unlock(&smc->clcsock_release_lock); + return -EBADF; + } if (unlikely(!smc->clcsock->ops->setsockopt)) rc = -EOPNOTSUPP; else @@ -2452,6 +2480,7 @@ static int smc_setsockopt(struct socket *sock, int level, int optname, sk->sk_err = smc->clcsock->sk->sk_err; sk_error_report(sk); } + mutex_unlock(&smc->clcsock_release_lock);
if (optlen < sizeof(int)) return -EINVAL; @@ -2468,7 +2497,7 @@ static int smc_setsockopt(struct socket *sock, int level, int optname, case TCP_FASTOPEN_NO_COOKIE: /* option not supported by SMC */ if (sk->sk_state == SMC_INIT && !smc->connect_nonblock) { - smc_switch_to_fallback(smc, SMC_CLC_DECL_OPTUNSUPP); + rc = smc_switch_to_fallback(smc, SMC_CLC_DECL_OPTUNSUPP); } else { rc = -EINVAL; } @@ -2511,13 +2540,23 @@ static int smc_getsockopt(struct socket *sock, int level, int optname, char __user *optval, int __user *optlen) { struct smc_sock *smc; + int rc;
smc = smc_sk(sock->sk); + mutex_lock(&smc->clcsock_release_lock); + if (!smc->clcsock) { + mutex_unlock(&smc->clcsock_release_lock); + return -EBADF; + } /* socket options apply to the CLC socket */ - if (unlikely(!smc->clcsock->ops->getsockopt)) + if (unlikely(!smc->clcsock->ops->getsockopt)) { + mutex_unlock(&smc->clcsock_release_lock); return -EOPNOTSUPP; - return smc->clcsock->ops->getsockopt(smc->clcsock, level, optname, - optval, optlen); + } + rc = smc->clcsock->ops->getsockopt(smc->clcsock, level, optname, + optval, optlen); + mutex_unlock(&smc->clcsock_release_lock); + return rc; }
static int smc_ioctl(struct socket *sock, unsigned int cmd,