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authorXie He <xie.he.0141@gmail.com>2020-12-28 05:53:39 +0300
committerDavid S. Miller <davem@davemloft.net>2020-12-29 02:09:04 +0300
commit1fef73597fa545c35fddc953979013882fbd4e55 (patch)
tree53dafb4464b51d40281343097c9698180d0eface /drivers/net/wan
parent9b22fece786ed641909988da4810bfa8e5d2e592 (diff)
downloadlinux-1fef73597fa545c35fddc953979013882fbd4e55.tar.xz
net: hdlc_ppp: Fix issues when mod_timer is called while timer is running
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> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/wan')
-rw-r--r--drivers/net/wan/hdlc_ppp.c7
1 files changed, 7 insertions, 0 deletions
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: