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

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: 3712b42d4b ("Add layer1 over IP support")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Duoming Zhou 2022-09-28 21:39:38 +08:00 committed by David S. Miller
parent 6ad1c94e1e
commit 2568a7e083
2 changed files with 8 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/isdn/mISDN/l1oip.h
View File

@ -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;

13
drivers/isdn/mISDN/l1oip_core.c
View File

@ -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 @@ multiframe:
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);