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Commit 466ed722 authored by Duoming Zhou's avatar Duoming Zhou Committed by Greg Kroah-Hartman
Browse files

mISDN: fix use-after-free bugs in l1oip timer handlers 



[ Upstream commit 2568a7e0832ee30b0a351016d03062ab4e0e0a3f ]

The l1oip_cleanup() traverses the l1oip_ilist and calls
release_card() to cleanup module and stack. However,
release_card() calls del_timer() to delete the timers
such as keep_tl and timeout_tl. If the timer handler is
running, the del_timer() will not stop it and result in
UAF bugs. One of the processes is shown below:

    (cleanup routine)          |        (timer handler)
release_card()                 | l1oip_timeout()
 ...                           |
 del_timer()                   | ...
 ...                           |
 kfree(hc) //FREE              |
                               | hc->timeout_on = 0 //USE

Fix by calling del_timer_sync() in release_card(), which
makes sure the timer handlers have finished before the
resources, such as l1oip and so on, have been deallocated.

What's more, the hc->workq and hc->socket_thread can kick
those timers right back in. We add a bool flag to show
if card is released. Then, check this flag in hc->workq
and hc->socket_thread.

Fixes: 3712b42d ("Add layer1 over IP support")
Signed-off-by: default avatarDuoming Zhou <duoming@zju.edu.cn>
Reviewed-by: default avatarLeon Romanovsky <leonro@nvidia.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent e6d0152c

drivers/isdn/mISDN/l1oip.h

+1 −0
Original line number Diff line number Diff line
@@ -59,6 +59,7 @@ struct l1oip { 
	int			bundle;		/* bundle channels in one frm */

	int			codec;		/* codec to use for transmis. */

	int			limit;		/* limit number of bchannels */

	bool			shutdown;	/* if card is released */



	/* timer */

	struct timer_list	keep_tl;

drivers/isdn/mISDN/l1oip_core.c

+7 −6
Original line number Diff line number Diff line
@@ -275,7 +275,7 @@ l1oip_socket_send(struct l1oip *hc, u8 localcodec, u8 channel, u32 chanmask, 
	p = frame;



	/* restart timer */

	if (time_before(hc->keep_tl.expires, jiffies + 5 * HZ))

	if (time_before(hc->keep_tl.expires, jiffies + 5 * HZ) && !hc->shutdown)

		mod_timer(&hc->keep_tl, jiffies + L1OIP_KEEPALIVE * HZ);

	else

		hc->keep_tl.expires = jiffies + L1OIP_KEEPALIVE * HZ;
@@ -601,7 +601,9 @@ l1oip_socket_parse(struct l1oip *hc, struct sockaddr_in *sin, u8 *buf, int len) 
		goto multiframe;



	/* restart timer */

	if (time_before(hc->timeout_tl.expires, jiffies + 5 * HZ) || !hc->timeout_on) {

	if ((time_before(hc->timeout_tl.expires, jiffies + 5 * HZ) ||

	     !hc->timeout_on) &&

	    !hc->shutdown) {

		hc->timeout_on = 1;

		mod_timer(&hc->timeout_tl, jiffies + L1OIP_TIMEOUT * HZ);

	} else /* only adjust timer */
@@ -1232,11 +1234,10 @@ release_card(struct l1oip *hc) 
{

	int	ch;



	if (timer_pending(&hc->keep_tl))

		del_timer(&hc->keep_tl);

	hc->shutdown = true;



	if (timer_pending(&hc->timeout_tl))

		del_timer(&hc->timeout_tl);

	del_timer_sync(&hc->keep_tl);

	del_timer_sync(&hc->timeout_tl);



	cancel_work_sync(&hc->workq);