KASAN: null-ptr-deref Write in io_uring_cancel_sqpoll

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    d01f2f7e Add linux-next specific files for 20210226
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=108dc5a8d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a1746d2802a82a05
dashboard link: https://syzkaller.appspot.com/bug?extid=be51ca5a4d97f017cd50

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+be51ca5a4d97f017cd50@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: null-ptr-deref in atomic_inc include/asm-generic/atomic-instrumented.h:240 [inline]
BUG: KASAN: null-ptr-deref in io_uring_cancel_sqpoll+0x2c7/0x450 fs/io_uring.c:8871
Write of size 4 at addr 0000000000000110 by task iou-sqp-19439/19447

CPU: 0 PID: 19447 Comm: iou-sqp-19439 Not tainted 5.11.0-next-20210226-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0xfa/0x151 lib/dump_stack.c:120
 __kasan_report mm/kasan/report.c:403 [inline]
 kasan_report.cold+0x5f/0xd8 mm/kasan/report.c:416
 check_region_inline mm/kasan/generic.c:180 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:186
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_inc include/asm-generic/atomic-instrumented.h:240 [inline]
 io_uring_cancel_sqpoll+0x2c7/0x450 fs/io_uring.c:8871
 io_sq_thread+0x1109/0x1ae0 fs/io_uring.c:6782
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 19447 Comm: iou-sqp-19439 Tainted: G    B             5.11.0-next-20210226-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0xfa/0x151 lib/dump_stack.c:120
 panic+0x306/0x73d kernel/panic.c:231
 end_report mm/kasan/report.c:102 [inline]
 end_report.cold+0x5a/0x5a mm/kasan/report.c:88
 __kasan_report mm/kasan/report.c:406 [inline]
 kasan_report.cold+0x6a/0xd8 mm/kasan/report.c:416
 check_region_inline mm/kasan/generic.c:180 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:186
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_inc include/asm-generic/atomic-instrumented.h:240 [inline]
 io_uring_cancel_sqpoll+0x2c7/0x450 fs/io_uring.c:8871
 io_sq_thread+0x1109/0x1ae0 fs/io_uring.c:6782
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Kernel Offset: disabled
Rebooting in 86400 seconds..


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