Messages in this thread | | | Date | Tue, 23 May 2023 18:14:18 +0200 | From | "Jason A. Donenfeld" <> | Subject | Re: [syzbot] [wireguard?] KASAN: slab-use-after-free Write in enqueue_timer |
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On Tue, May 23, 2023 at 09:05:12AM -0700, Jakub Kicinski wrote: > On Tue, 23 May 2023 17:46:20 +0200 Jason A. Donenfeld wrote: > > > Freed by task 41: > > > __kmem_cache_free+0x264/0x3c0 mm/slub.c:3799 > > > device_release+0x95/0x1c0 > > > kobject_cleanup lib/kobject.c:683 [inline] > > > kobject_release lib/kobject.c:714 [inline] > > > kref_put include/linux/kref.h:65 [inline] > > > kobject_put+0x228/0x470 lib/kobject.c:731 > > > netdev_run_todo+0xe5a/0xf50 net/core/dev.c:10400 > > > > So that means the memory in question is actually the one that's > > allocated and freed by the networking stack. Specifically, dev.c:10626 > > is allocating a struct net_device with a trailing struct wg_device (its > > priv_data). However, wg_device does not have any struct timer_lists in > > it, and I don't see how net_device's watchdog_timer would be related to > > the stacktrace which is clearly operating over a wg_peer timer. > > > > So what on earth is going on here? > > Your timer had the pleasure of getting queued _after_ a dead watchdog > timer, no? IOW it tries to update the ->next pointer of a queued > watchdog timer.
Ahh, you're right! Specifically,
> hlist_add_head include/linux/list.h:945 [inline] > enqueue_timer+0xad/0x560 kernel/time/timer.c:605
The write on line 945 refers to the side of the timer base, not the peer's timer_list being queued. So indeed, the wireguard netdev is still alive at this point, but it's being queued to a timer in a different netdev that's already been freed (whether watchdog or otherwise in some privdata). So, IOW, not a wireguard bug, right?
Jason
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