* [PATCH net v2] net: hdlc_ppp: Fix issues when mod_timer is called while timer is running
@ 2020-12-28 2:53 Xie He
2020-12-28 23:11 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: Xie He @ 2020-12-28 2:53 UTC (permalink / raw)
To: David S. Miller, Jakub Kicinski, netdev, linux-kernel, Krzysztof Halasa
Cc: Xie He
ppp_cp_event is called directly or indirectly by ppp_rx with "ppp->lock"
held. It may call mod_timer to add a new timer. However, at the same time
ppp_timer may be already running and waiting for "ppp->lock". In this
case, there's no need for ppp_timer to continue running and it can just
exit.
If we let ppp_timer continue running, it may call add_timer. This causes
kernel panic because add_timer can't be called with a timer pending.
This patch fixes this problem.
Fixes: e022c2f07ae5 ("WAN: new synchronous PPP implementation for generic HDLC.")
Cc: Krzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
---
drivers/net/wan/hdlc_ppp.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/net/wan/hdlc_ppp.c b/drivers/net/wan/hdlc_ppp.c
index 64f855651336..261b53fc8e04 100644
--- a/drivers/net/wan/hdlc_ppp.c
+++ b/drivers/net/wan/hdlc_ppp.c
@@ -569,6 +569,13 @@ static void ppp_timer(struct timer_list *t)
unsigned long flags;
spin_lock_irqsave(&ppp->lock, flags);
+ /* mod_timer could be called after we entered this function but
+ * before we got the lock.
+ */
+ if (timer_pending(&proto->timer)) {
+ spin_unlock_irqrestore(&ppp->lock, flags);
+ return;
+ }
switch (proto->state) {
case STOPPING:
case REQ_SENT:
--
2.27.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH net v2] net: hdlc_ppp: Fix issues when mod_timer is called while timer is running
2020-12-28 2:53 [PATCH net v2] net: hdlc_ppp: Fix issues when mod_timer is called while timer is running Xie He
@ 2020-12-28 23:11 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2020-12-28 23:11 UTC (permalink / raw)
To: xie.he.0141; +Cc: kuba, netdev, linux-kernel, khc
From: Xie He <xie.he.0141@gmail.com>
Date: Sun, 27 Dec 2020 18:53:39 -0800
> ppp_cp_event is called directly or indirectly by ppp_rx with "ppp->lock"
> held. It may call mod_timer to add a new timer. However, at the same time
> ppp_timer may be already running and waiting for "ppp->lock". In this
> case, there's no need for ppp_timer to continue running and it can just
> exit.
>
> If we let ppp_timer continue running, it may call add_timer. This causes
> kernel panic because add_timer can't be called with a timer pending.
> This patch fixes this problem.
>
> Fixes: e022c2f07ae5 ("WAN: new synchronous PPP implementation for generic HDLC.")
> Cc: Krzysztof Halasa <khc@pm.waw.pl>
> Signed-off-by: Xie He <xie.he.0141@gmail.com>
Applied and queued up for -stable, thanks!
^ permalink raw reply [flat|nested] 2+ messages in thread
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2020-12-28 23:11 ` David Miller
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