lkml.org 
[lkml]   [2022]   [Sep]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH V3] mISDN: fix use-after-free bugs in l1oip timer handlers
Date
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 use del_timer_sync(&hc->keep_tl)
and cancel_work_sync(&hc->workq) twice to stop keep_tl timer
and hc->workq. Then, we add del_timer_sync(&hc->timeout_tl)
inside l1oip_socket_close() to stop timeout_tl timer. Because
the hc->socket_thread has been killed and the timeout_tl timer
will not be rescheduled.

Fixes: 3712b42d4b1b ("Add layer1 over IP support")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
---
Changes in v3:
- Make commit messages more clearer.
- Add del_timer_sync(&hc->timeout_tl) inside l1oip_socket_close().

drivers/isdn/mISDN/l1oip_core.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/isdn/mISDN/l1oip_core.c b/drivers/isdn/mISDN/l1oip_core.c
index 2c40412466e..5939f1d8f08 100644
--- a/drivers/isdn/mISDN/l1oip_core.c
+++ b/drivers/isdn/mISDN/l1oip_core.c
@@ -762,6 +762,8 @@ l1oip_socket_close(struct l1oip *hc)
wait_for_completion(&hc->socket_complete);
}

+ del_timer_sync(&hc->timeout_tl);
+
/* if active, we send up a PH_DEACTIVATE and deactivate */
if (test_bit(FLG_ACTIVE, &dch->Flags)) {
if (debug & (DEBUG_L1OIP_MSG | DEBUG_L1OIP_SOCKET))
@@ -1232,12 +1234,10 @@ release_card(struct l1oip *hc)
{
int ch;

- if (timer_pending(&hc->keep_tl))
- del_timer(&hc->keep_tl);
-
- 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);
+ del_timer_sync(&hc->keep_tl);
cancel_work_sync(&hc->workq);

if (hc->socket_thread)
--
2.17.1
\
 
 \ /
  Last update: 2022-09-24 04:19    [W:0.051 / U:0.636 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site