From: Duoming Zhou <duoming@zju.edu.cn> stable inclusion from stable-4.19.239 commit 753b9d220a7d36dac70e7c6d05492d10d6f9dd36 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I62KQZ CVE: CVE-2022-41858 -------------------------------- [ Upstream commit ec4eb8a86ade4d22633e1da2a7d85a846b7d1798 ] When a slip driver is detaching, the slip_close() will act to cleanup necessary resources and sl->tty is set to NULL in slip_close(). Meanwhile, the packet we transmit is blocked, sl_tx_timeout() will be called. Although slip_close() and sl_tx_timeout() use sl->lock to synchronize, we don`t judge whether sl->tty equals to NULL in sl_tx_timeout() and the null pointer dereference bug will happen. (Thread 1) | (Thread 2) | slip_close() | spin_lock_bh(&sl->lock) | ... ... | sl->tty = NULL //(1) sl_tx_timeout() | spin_unlock_bh(&sl->lock) spin_lock(&sl->lock); | ... | ... tty_chars_in_buffer(sl->tty)| if (tty->ops->..) //(2) | ... | synchronize_rcu() We set NULL to sl->tty in position (1) and dereference sl->tty in position (2). This patch adds check in sl_tx_timeout(). If sl->tty equals to NULL, sl_tx_timeout() will goto out. Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> Reviewed-by: Jiri Slaby <jirislaby@kernel.org> Link: https://lore.kernel.org/r/20220405132206.55291-1-duoming@zju.edu.cn Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Liu Jian <liujian56@huawei.com> Reviewed-by: Yue Haibing <yuehaibing@huawei.com> Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com> Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com> --- drivers/net/slip/slip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c index 93f303ec17e2..a959e01610b1 100644 --- a/drivers/net/slip/slip.c +++ b/drivers/net/slip/slip.c @@ -471,7 +471,7 @@ static void sl_tx_timeout(struct net_device *dev) spin_lock(&sl->lock); if (netif_queue_stopped(dev)) { - if (!netif_running(dev)) + if (!netif_running(dev) || !sl->tty) goto out; /* May be we must check transmitter timeout here ? -- 2.25.1