=============================
WARNING: suspicious RCU usage
5.9.0-next-20201016-syzkaller #0 Not tainted
-----------------------------
include/linux/cgroup.h:494 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
no locks held by syz-executor.1/8617.

stack backtrace:
CPU: 0 PID: 8617 Comm: syz-executor.1 Not tainted 5.9.0-next-20201016-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fb lib/dump_stack.c:118
 task_css include/linux/cgroup.h:494 [inline]
 blkcg_css include/linux/blk-cgroup.h:224 [inline]
 blkcg_css include/linux/blk-cgroup.h:217 [inline]
 io_init_identity+0x3a9/0x450 fs/io_uring.c:1052
 io_uring_alloc_task_context+0x176/0x250 fs/io_uring.c:7730
 io_uring_add_task_file+0x10d/0x180 fs/io_uring.c:8653
 io_uring_get_fd fs/io_uring.c:9144 [inline]
 io_uring_create fs/io_uring.c:9308 [inline]
 io_uring_setup+0x2727/0x3660 fs/io_uring.c:9342
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45de59
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff783089bf8 EFLAGS: 00000206 ORIG_RAX: 00000000000001a9
RAX: ffffffffffffffda RBX: 00000000200001c0 RCX: 000000000045de59
RDX: 0000000020ffc000 RSI: 00000000200001c0 RDI: 0000000000000001
RBP: 000000000118bf78 R08: 0000000020000280 R09: 0000000020000280
R10: 0000000020000240 R11: 0000000000000206 R12: 0000000020ffc000
R13: 0000000020ffb000 R14: 0000000020000280 R15: 0000000020000240
BUG: using __this_cpu_read() in preemptible [00000000] code: syz-executor.1/8617
caller is lockdep_hardirqs_on_prepare+0x5e/0x450 kernel/locking/lockdep.c:4060
CPU: 1 PID: 8617 Comm: syz-executor.1 Not tainted 5.9.0-next-20201016-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fb lib/dump_stack.c:118
 check_preemption_disabled+0x128/0x130 lib/smp_processor_id.c:48
 lockdep_hardirqs_on_prepare+0x5e/0x450 kernel/locking/lockdep.c:4060
 trace_hardirqs_on+0x5b/0x1c0 kernel/trace/trace_preemptirq.c:49
 __bad_area_nosemaphore+0xc6/0x4f0 arch/x86/mm/fault.c:797
 do_user_addr_fault+0x852/0xbf0 arch/x86/mm/fault.c:1335
 handle_page_fault arch/x86/mm/fault.c:1429 [inline]
 exc_page_fault+0xa8/0x190 arch/x86/mm/fault.c:1482
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:583
RIP: 0033:0x457a5f
Code: bc d1 f3 0f 7f 27 f3 0f 7f 6f 10 f3 0f 7f 77 20 f3 0f 7f 7f 30 49 83 c0 0f 49 29 d0 48 8d 7c 17 31 e9 95 0b 00 00 66 0f ef c0 <f3> 0f 6f 0e f3 0f 6f 56 10 66 0f 74 c1 66 0f d7 d0 49 83 f8 11 0f
RSP: 002b:00007ff783089828 EFLAGS: 00010283
RAX: 00007ff783089850 RBX: 6666666666666667 RCX: 0000000000000000
RDX: 00000000000003ff RSI: 0000000000000000 RDI: 00007ff783089850
RBP: 000000000118bf60 R08: 00000000000003ff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffff60121cf R14: 00007ff78308a9c0 R15: 000000000118bf2c
BUG: using __this_cpu_read() in preemptible [00000000] code: syz-executor.1/8617
caller is lockdep_hardirqs_on+0x34/0x110 kernel/locking/lockdep.c:4129
CPU: 1 PID: 8617 Comm: syz-executor.1 Not tainted 5.9.0-next-20201016-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fb lib/dump_stack.c:118
 check_preemption_disabled+0x128/0x130 lib/smp_processor_id.c:48
 lockdep_hardirqs_on+0x34/0x110 kernel/locking/lockdep.c:4129
 __bad_area_nosemaphore+0xc6/0x4f0 arch/x86/mm/fault.c:797
 do_user_addr_fault+0x852/0xbf0 arch/x86/mm/fault.c:1335
 handle_page_fault arch/x86/mm/fault.c:1429 [inline]
 exc_page_fault+0xa8/0x190 arch/x86/mm/fault.c:1482
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:583
RIP: 0033:0x457a5f
Code: bc d1 f3 0f 7f 27 f3 0f 7f 6f 10 f3 0f 7f 77 20 f3 0f 7f 7f 30 49 83 c0 0f 49 29 d0 48 8d 7c 17 31 e9 95 0b 00 00 66 0f ef c0 <f3> 0f 6f 0e f3 0f 6f 56 10 66 0f 74 c1 66 0f d7 d0 49 83 f8 11 0f
RSP: 002b:00007ff783089828 EFLAGS: 00010283
RAX: 00007ff783089850 RBX: 6666666666666667 RCX: 0000000000000000
RDX: 00000000000003ff RSI: 0000000000000000 RDI: 00007ff783089850
RBP: 000000000118bf60 R08: 00000000000003ff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffff60121cf R14: 00007ff78308a9c0 R15: 000000000118bf2c