=============================
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.2/9737.

stack backtrace:
CPU: 0 PID: 9737 Comm: syz-executor.2 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:00007f6b756eec78 EFLAGS: 00000246 ORIG_RAX: 00000000000001a9
RAX: ffffffffffffffda RBX: 00000000000085c0 RCX: 000000000045de59
RDX: 0000000000000000 RSI: 00000000200003c0 RDI: 000000000000261f
RBP: 000000000118bf58 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffe7b2e806f R14: 00007f6b756ef9c0 R15: 000000000118bf2c