[PATCH net] net/smc: Transitional solution for clcsock race issue
From: Wen Gu
Date: Thu Jan 13 2022 - 10:03:17 EST
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.
Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
---
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 12c52c7..c625af3 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)
@@ -1518,11 +1535,12 @@ 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);
@@ -1964,8 +1982,11 @@ 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;
}
@@ -2254,7 +2275,9 @@ 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;
@@ -2447,6 +2470,11 @@ 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
@@ -2456,6 +2484,7 @@ 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;
@@ -2472,7 +2501,7 @@ 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;
}
@@ -2515,13 +2544,23 @@ 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,
--
1.8.3.1