Messages in this thread Patch in this message | | | From | Duoming Zhou <> | Subject | [PATCH net] net: rose: fix UAF bug caused by rose_t0timer_expiry | Date | Thu, 30 Jun 2022 22:38:42 +0800 |
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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 del_timer() in rose_stop_t0timer() and rose_stop_ftimer() 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> --- net/rose/rose_link.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/rose/rose_link.c b/net/rose/rose_link.c index 8b96a56d3a4..9734d1264de 100644 --- a/net/rose/rose_link.c +++ b/net/rose/rose_link.c @@ -54,12 +54,12 @@ static void rose_start_t0timer(struct rose_neigh *neigh) void rose_stop_ftimer(struct rose_neigh *neigh) { - del_timer(&neigh->ftimer); + del_timer_sync(&neigh->ftimer); } void rose_stop_t0timer(struct rose_neigh *neigh) { - del_timer(&neigh->t0timer); + del_timer_sync(&neigh->t0timer); } int rose_ftimer_running(struct rose_neigh *neigh) -- 2.17.1
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