On Tue, May 23, 2023 at 09:47:36AM -0700, Jakub Kicinski wrote: > On Tue, 23 May 2023 18:42:53 +0200 Jason A. Donenfeld wrote: > > > It should, no idea why it isn't. Looking thru the code now I don't see > > > any obvious gaps where timer object is on a list but not active :S > > > There's no way to get a vmcore from syzbot, right? :) > > > > > > Also I thought the shutdown leads to a warning when someone tries to > > > schedule the dead timer but in fact add_timer() just exits cleanly. > > > So the shutdown won't help us find the culprit :( > > > > Worth noting that it could also be caused by adding to a dead timer > > anywhere in priv_data of another netdev, not just the sole timer_list > > in net_device. > > Oh, I thought you zero'ed in on the watchdog based on offsets. > Still, object debug should track all timers in the slab and complain > on the free path.
No, I mentioned watchdog because it's the only timer_list in struct net_device. Offset analysis is an interesting idea though. Look at this: > The buggy address belongs to the object at ffff88801ecc0000 > which belongs to the cache kmalloc-cg-8k of size 8192 > The buggy address is located 5376 bytes inside of > freed 8192-byte region [ffff88801ecc0000, ffff88801ecc2000) IDA says that for syzkaller's vmlinux, net_device has a size of 0xc80 and wg_device has a size of 0x880. 0xc80+0x880=5376. Coincidence that the address offset is just after what wg uses? Hm. Jason
