netdev - [PATCH net] drivers: net: can: Fix deadlock in grcan

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 25 Apr 2022 12:24:00 +0800
From:   Duoming Zhou <duoming@....edu.cn>
To:     linux-kernel@...r.kernel.org
Cc:     wg@...ndegger.com, mkl@...gutronix.de, davem@...emloft.net,
        kuba@...nel.org, pabeni@...hat.com, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, Duoming Zhou <duoming@....edu.cn>
Subject: [PATCH net] drivers: net: can: Fix deadlock in grcan_close()

There are deadlocks caused by del_timer_sync(&priv->hang_timer)
and del_timer_sync(&priv->rr_timer) in grcan_close(), one of
the deadlocks are shown below:

   (Thread 1)              |      (Thread 2)
                           | grcan_reset_timer()
grcan_close()              |  mod_timer()
 spin_lock_irqsave() //(1) |  (wait a time)
 ...                       | grcan_initiate_running_reset()
 del_timer_sync()          |  spin_lock_irqsave() //(2)
 (wait timer to stop)      |  ...

We hold priv->lock in position (1) of thread 1 and use
del_timer_sync() to wait timer to stop, but timer handler
also need priv->lock in position (2) of thread 2.
As a result, grcan_close() will block forever.

This patch extracts del_timer_sync() from the protection of
spin_lock_irqsave(), which could let timer handler to obtain
the needed lock.

Signed-off-by: Duoming Zhou <duoming@....edu.cn>
---
 drivers/net/can/grcan.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/can/grcan.c b/drivers/net/can/grcan.c
index d0c5a7a60da..1189057b5d6 100644
--- a/drivers/net/can/grcan.c
+++ b/drivers/net/can/grcan.c
@@ -1102,8 +1102,10 @@ static int grcan_close(struct net_device *dev)
 
 	priv->closing = true;
 	if (priv->need_txbug_workaround) {
+		spin_unlock_irqrestore(&priv->lock, flags);
 		del_timer_sync(&priv->hang_timer);
 		del_timer_sync(&priv->rr_timer);
+		spin_lock_irqsave(&priv->lock, flags);
 	}
 	netif_stop_queue(dev);
 	grcan_stop_hardware(dev);
-- 
2.17.1