From: Duoming Zhou duoming@zju.edu.cn
commit 148ca04518070910739dfc4eeda765057856403d upstream.
There are UAF bugs caused by rose_t0timer_expiry(). The root cause is that del_timer() could not stop the timer handler that is running and there is no synchronization. One of the race conditions is shown below:
(thread 1) | (thread 2) | rose_device_event | rose_rt_device_down | rose_remove_neigh rose_t0timer_expiry | rose_stop_t0timer(rose_neigh) ... | del_timer(&neigh->t0timer) | kfree(rose_neigh) //[1]FREE neigh->dce_mode //[2]USE |
The rose_neigh is deallocated in position [1] and use in position [2].
The crash trace triggered by POC is like below:
BUG: KASAN: use-after-free in expire_timers+0x144/0x320 Write of size 8 at addr ffff888009b19658 by task swapper/0/0 ... Call Trace: <IRQ> dump_stack_lvl+0xbf/0xee print_address_description+0x7b/0x440 print_report+0x101/0x230 ? expire_timers+0x144/0x320 kasan_report+0xed/0x120 ? expire_timers+0x144/0x320 expire_timers+0x144/0x320 __run_timers+0x3ff/0x4d0 run_timer_softirq+0x41/0x80 __do_softirq+0x233/0x544 ...
This patch changes rose_stop_ftimer() and rose_stop_t0timer() in rose_remove_neigh() to del_timer_sync() in order that the timer handler could be finished before the resources such as rose_neigh and so on are deallocated. As a result, the UAF bugs could be mitigated.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Duoming Zhou duoming@zju.edu.cn Link: https://lore.kernel.org/r/20220705125610.77971-1-duoming@zju.edu.cn Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/rose/rose_route.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/rose/rose_route.c +++ b/net/rose/rose_route.c @@ -230,8 +230,8 @@ static void rose_remove_neigh(struct ros { struct rose_neigh *s;
- rose_stop_ftimer(rose_neigh); - rose_stop_t0timer(rose_neigh); + del_timer_sync(&rose_neigh->ftimer); + del_timer_sync(&rose_neigh->t0timer);
skb_queue_purge(&rose_neigh->queue);