Messages in this thread | | | From | Eric Dumazet <> | Date | Tue, 23 May 2023 19:07:05 +0200 | Subject | Re: [syzbot] [wireguard?] KASAN: slab-use-after-free Write in enqueue_timer |
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On Tue, May 23, 2023 at 7:05 PM Eric Dumazet <edumazet@google.com> wrote: > > On Tue, May 23, 2023 at 7:01 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote: > > > > 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? > > > Note that the syzkaller report mentioned: > > alloc_netdev_mqs+0x89/0xf30 net/core/dev.c:10626 > usbnet_probe+0x196/0x2770 drivers/net/usb/usbnet.c:1698 > usb_probe_interface+0x5c4/0xb00 drivers/usb/core/driver.c:396 > really_probe+0x294/0xc30 drivers/base/dd.c:658 > __driver_probe_device+0x1a2/0x3d0 drivers/base/dd.c:800 > driver_probe_device+0x50/0x420 drivers/base/dd.c:830 > __device_attach_driver+0x2d3/0x520 drivers/base/dd.c:958 > > So maybe an usbnet driver has a timer_list in its priv_data.
struct usbnet { ... struct timer_list delay;
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