On Wed, Oct 7, 2020 at 3:56 PM Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> wrote: > > On 10/5/20 2:44 PM, Shuah Khan wrote: > > On 10/5/20 8:04 AM, Andrey Konovalov wrote: > >> On Mon, Oct 5, 2020 at 3:59 PM syzbot > >> <syzbot+bf1a360e305ee719e364@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > >>> > >>> Hello, > >>> > >>> syzbot found the following issue on: > >>> > >>> HEAD commit: d3d45f82 Merge tag 'pinctrl-v5.9-2' of > >>> git://git.kernel.or.. > >>> git tree: upstream > >>> console output: https://syzkaller.appspot.com/x/log.txt?x=15781d8f900000 > >>> kernel config: > >>> https://syzkaller.appspot.com/x/.config?x=89ab6a0c48f30b49 > >>> dashboard link: > >>> https://syzkaller.appspot.com/bug?extid=bf1a360e305ee719e364 > >>> compiler: gcc (GCC) 10.1.0-syz 20200507 > >>> syz repro: > >>> https://syzkaller.appspot.com/x/repro.syz?x=16cbaa7d900000 > >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1364f367900000 > >>> > >>> IMPORTANT: if you fix the issue, please add the following tag to the > >>> commit: > >>> Reported-by: syzbot+bf1a360e305ee719e364@xxxxxxxxxxxxxxxxxxxxxxxxx > >>> > >>> vhci_hcd: stop threads > >>> vhci_hcd: release socket > >>> vhci_hcd: disconnect device > >>> ================================================================== > >>> BUG: KASAN: null-ptr-deref in instrument_atomic_write > >>> include/linux/instrumented.h:71 [inline] > >>> BUG: KASAN: null-ptr-deref in atomic_fetch_add_relaxed > >>> include/asm-generic/atomic-instrumented.h:142 [inline] > >>> BUG: KASAN: null-ptr-deref in refcount_add > >>> include/linux/refcount.h:201 [inline] > >>> BUG: KASAN: null-ptr-deref in refcount_inc > >>> include/linux/refcount.h:241 [inline] > >>> BUG: KASAN: null-ptr-deref in get_task_struct > >>> include/linux/sched/task.h:104 [inline] > >>> BUG: KASAN: null-ptr-deref in kthread_stop+0x90/0x7e0 > >>> kernel/kthread.c:591 > >>> Write of size 4 at addr 000000000000001c by task kworker/u4:5/2519 > >>> > >>> CPU: 1 PID: 2519 Comm: kworker/u4:5 Not tainted 5.9.0-rc7-syzkaller #0 > >>> Hardware name: Google Google Compute Engine/Google Compute Engine, > >>> BIOS Google 01/01/2011 > >>> Workqueue: usbip_event event_handler > >>> Call Trace: > >>> __dump_stack lib/dump_stack.c:77 [inline] > >>> dump_stack+0x198/0x1fd lib/dump_stack.c:118 > >>> __kasan_report mm/kasan/report.c:517 [inline] > >>> kasan_report.cold+0x5/0x37 mm/kasan/report.c:530 > >>> check_memory_region_inline mm/kasan/generic.c:186 [inline] > >>> check_memory_region+0x13d/0x180 mm/kasan/generic.c:192 > >>> instrument_atomic_write include/linux/instrumented.h:71 [inline] > >>> atomic_fetch_add_relaxed > >>> include/asm-generic/atomic-instrumented.h:142 [inline] > >>> refcount_add include/linux/refcount.h:201 [inline] > >>> refcount_inc include/linux/refcount.h:241 [inline] > >>> get_task_struct include/linux/sched/task.h:104 [inline] > >>> kthread_stop+0x90/0x7e0 kernel/kthread.c:591 > >>> vhci_shutdown_connection+0x170/0x2a0 drivers/usb/usbip/vhci_hcd.c:1015 > >>> event_handler+0x1a5/0x450 drivers/usb/usbip/usbip_event.c:78 > >>> process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 > >>> worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 > >>> kthread+0x3b5/0x4a0 kernel/kthread.c:292 > >>> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 > >>> ================================================================== > >>> Kernel panic - not syncing: panic_on_warn set ... > >>> CPU: 1 PID: 2519 Comm: kworker/u4:5 Tainted: G B > >>> 5.9.0-rc7-syzkaller #0 > >>> Hardware name: Google Google Compute Engine/Google Compute Engine, > >>> BIOS Google 01/01/2011 > >>> Workqueue: usbip_event event_handler > >>> Call Trace: > >>> __dump_stack lib/dump_stack.c:77 [inline] > >>> dump_stack+0x198/0x1fd lib/dump_stack.c:118 > >>> panic+0x382/0x7fb kernel/panic.c:231 > >>> end_report+0x4d/0x53 mm/kasan/report.c:104 > >>> __kasan_report mm/kasan/report.c:520 [inline] > >>> kasan_report.cold+0xd/0x37 mm/kasan/report.c:530 > >>> check_memory_region_inline mm/kasan/generic.c:186 [inline] > >>> check_memory_region+0x13d/0x180 mm/kasan/generic.c:192 > >>> instrument_atomic_write include/linux/instrumented.h:71 [inline] > >>> atomic_fetch_add_relaxed > >>> include/asm-generic/atomic-instrumented.h:142 [inline] > >>> refcount_add include/linux/refcount.h:201 [inline] > >>> refcount_inc include/linux/refcount.h:241 [inline] > >>> get_task_struct include/linux/sched/task.h:104 [inline] > >>> kthread_stop+0x90/0x7e0 kernel/kthread.c:591 > >>> vhci_shutdown_connection+0x170/0x2a0 drivers/usb/usbip/vhci_hcd.c:1015 > >>> event_handler+0x1a5/0x450 drivers/usb/usbip/usbip_event.c:78 > >>> process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 > >>> worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 > >>> kthread+0x3b5/0x4a0 kernel/kthread.c:292 > >>> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 > >>> Kernel Offset: disabled > >>> Rebooting in 86400 seconds.. > >> > >> Hi Valentina and Shuah, > >> > >> There appears to be a race condition in the USB/IP vhci_hcd shutdown > >> procedure. It happens quite often during fuzzing with syzkaller, and > >> prevents us from going deeper into the USB/IP code. > >> > >> Could you advise us what would be the best fix for this? > >> > > > > Hi Andrey, > > > > Reading the comments for this routine, looks like there is an assumption > > that context begins cleanup and race conditions aren't considered. > > > > The right fix is holding vhci->lock and vdev->priv_lock to protect > > critical sections in this routine. I will send a patch for this. > > > > Hi Andrey, > > I have been unable to reproduce the problem with the reproducer > so far. You mentioned it happens quite often. > > - matched config with yours > - load vhci_hcd module and run the reproducer Hm, if you matched the config, then the module should be built-in? > > I do see the messages during shutdown - stop threads etc. > > What am I missing? This appears to be a race that requires precise timings. I failed to reproduce it with the C reproducer, but I managed to reproduce it with the syzkaller repro program: https://syzkaller.appspot.com/x/repro.syz?x=16cbaa7d900000 To do that you need to build syzkaller, and copy ./bin/syz-execprog and ./bin/syz-executor into your testing environment, and then do: ./syz-execprog -sandbox=none -repeat=0 -procs=6 ./repro.prog Thanks!
