[PATCH 4.14 44/78] drivers: net: hippi: Fix deadlock in rr_close()

Greg Kroah-Hartman
2022-05-10T13:23:50Z

From: Duoming Zhou <duoming@zju.edu.cn>

[ Upstream commit bc6de2878429e85c1f1afaa566f7b5abb2243eef ]

There is a deadlock in rr_close(), which is shown below:

(Thread 1) | (Thread 2)
| rr_open()
rr_close() | add_timer()
spin_lock_irqsave() //(1) | (wait a time)
... | rr_timer()
del_timer_sync() | spin_lock_irqsave() //(2)
(wait timer to stop) | ...

We hold rrpriv->lock in position (1) of thread 1 and
use del_timer_sync() to wait timer to stop, but timer handler
also need rrpriv->lock in position (2) of thread 2.
As a result, rr_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@zju.edu.cn>
Link: https://lore.kernel.org/r/20220417125519.82618-1-duoming@zju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/hippi/rrunner.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/net/hippi/rrunner.c b/drivers/net/hippi/rrunner.c
index 40ef4aeb0ef0..3a73ac03fb2b 100644
--- a/drivers/net/hippi/rrunner.c
+++ b/drivers/net/hippi/rrunner.c
@@ -1354,7 +1354,9 @@ static int rr_close(struct net_device *dev)

rrpriv->fw_running = 0;

+ spin_unlock_irqrestore(&rrpriv->lock, flags);
del_timer_sync(&rrpriv->timer);
+ spin_lock_irqsave(&rrpriv->lock, flags);

writel(0, &regs->TxPi);
writel(0, &regs->IpRxPi);
--
2.35.1