[PATCH 5.4 72/84] drivers: net: hippi: Fix deadlock in rr_close()

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 a4b3fce69ecd..6016e182f008 100644 --- a/drivers/net/hippi/rrunner.c +++ b/drivers/net/hippi/rrunner.c @@ -1346,7 +1346,9 @@ 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);