Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: KASAN: null-ptr-deref Write in vhci_shutdown_connection ================================================================== 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+0x90/0x810 kernel/kthread.c:591 Write of size 4 at addr 000000000000001c by task kworker/u4:4/186 CPU: 0 PID: 186 Comm: kworker/u4:4 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+0x107/0x16e 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+0x90/0x810 kernel/kthread.c:591 vhci_shutdown_connection+0x17f/0x360 drivers/usb/usbip/vhci_hcd.c:1015 event_handler+0x1f0/0x4f0 drivers/usb/usbip/usbip_event.c:78 process_one_work+0x86c/0x16a0 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: 0 PID: 186 Comm: kworker/u4:4 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+0x107/0x16e lib/dump_stack.c:118 panic+0x393/0x7d3 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+0x90/0x810 kernel/kthread.c:591 vhci_shutdown_connection+0x17f/0x360 drivers/usb/usbip/vhci_hcd.c:1015 event_handler+0x1f0/0x4f0 drivers/usb/usbip/usbip_event.c:78 process_one_work+0x86c/0x16a0 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.. Tested on: commit: d3d45f82 Merge tag 'pinctrl-v5.9-2' of git://git.kerne.. git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ console output: https://syzkaller.appspot.com/x/log.txt?x=125b4faa700000 kernel config: https://syzkaller.appspot.com/x/.config?x=c4f7c05cb42b5045 dashboard link: https://syzkaller.appspot.com/bug?extid=31ae6d17d115e980fd14 compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 patch: https://syzkaller.appspot.com/x/patch.diff?x=1359552c700000
