Messages in this thread Patch in this message | | | From | Duoming Zhou <> | Subject | [PATCH V2] mISDN: fix use-after-free bugs in l1oip timer handlers | Date | Fri, 23 Sep 2022 22:25:14 +0800 |
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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->keep_tl) twice to stop keep_tl timer and hc->workq. Then, we add del_timer_sync(&hc->timeout_tl) behind l1oip_socket_close() to stop timeout_tl timer.
Fixes: 3712b42d4b1b ("Add layer1 over IP support") Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- Changes in v2: - Solve the problem that timers could be restarted by other threads.
drivers/isdn/mISDN/l1oip_core.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/drivers/isdn/mISDN/l1oip_core.c b/drivers/isdn/mISDN/l1oip_core.c index 2c40412466e..7b89d98a781 100644 --- a/drivers/isdn/mISDN/l1oip_core.c +++ b/drivers/isdn/mISDN/l1oip_core.c @@ -1232,17 +1232,16 @@ 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); + cancel_work_sync(&hc->workq); + del_timer_sync(&hc->keep_tl); cancel_work_sync(&hc->workq); if (hc->socket_thread) l1oip_socket_close(hc); + del_timer_sync(&hc->timeout_tl); + if (hc->registered && hc->chan[hc->d_idx].dch) mISDN_unregister_device(&hc->chan[hc->d_idx].dch->dev); for (ch = 0; ch < 128; ch++) { -- 2.17.1
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