From: Xie He xie.he.0141@gmail.com
[ Upstream commit 1fef73597fa545c35fddc953979013882fbd4e55 ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/wan/hdlc_ppp.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/drivers/net/wan/hdlc_ppp.c +++ b/drivers/net/wan/hdlc_ppp.c @@ -572,6 +572,13 @@ static void ppp_timer(unsigned long arg) 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: