[PATCH 5.4 326/389] atm: idt77252: fix use-after-free bugs caused by tst_timer

Greg Kroah-Hartman
2022-08-23T11:59:45Z

From: Duoming Zhou <duoming@zju.edu.cn>

commit 3f4093e2bf4673f218c0bf17d8362337c400e77b upstream.

There are use-after-free bugs caused by tst_timer. The root cause
is that there are no functions to stop tst_timer in idt77252_exit().
One of the possible race conditions is shown below:

(thread 1) | (thread 2)
| idt77252_init_one
| init_card
| fill_tst
| mod_timer(&card->tst_timer, ...)
idt77252_exit | (wait a time)
| tst_timer
|
| ...
kfree(card) // FREE |
| card->soft_tst[e] // USE

The idt77252_dev is deallocated in idt77252_exit() and used in
timer handler.

This patch adds del_timer_sync() in idt77252_exit() in order that
the timer handler could be stopped before the idt77252_dev is
deallocated.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20220805070008.18007-1-duoming@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/atm/idt77252.c | 1 +
1 file changed, 1 insertion(+)

--- a/drivers/atm/idt77252.c
+++ b/drivers/atm/idt77252.c
@@ -3766,6 +3766,7 @@ static void __exit idt77252_exit(void)
card = idt77252_chain;
dev = card->atmdev;
idt77252_chain = card->next;
+ del_timer_sync(&card->tst_timer);

if (dev->phy->stop)
dev->phy->stop(dev);