=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
lib/maple_tree.c:720 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
locks held by syz.0.17/5918: 1, last CPU#1:
 #0: ffff8880375320a0 (&ctx->uring_lock){+.+.}-{4:4}, at: tctx_task_work_run+0x1cd/0xbf0 io_uring/tw.c:92

stack backtrace:
CPU: 1 UID: 0 PID: 5918 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 lockdep_rcu_suspicious.cold+0x4f/0xb2 kernel/locking/lockdep.c:6972
 mas_root lib/maple_tree.c:720 [inline]
 mas_start+0x621/0x7c0 lib/maple_tree.c:1250
 mas_state_walk lib/maple_tree.c:3006 [inline]
 mas_walk+0x82/0x310 lib/maple_tree.c:4458
 ublk_try_buf_match+0x469/0x7e0 drivers/block/ublk_drv.c:5639
 ublk_init_iod+0x4a4/0x5b0 drivers/block/ublk_drv.c:521
 ublk_setup_iod+0x145/0x2f0 drivers/block/ublk_drv.c:1536
 ublk_dispatch_req+0x4e/0xb00 drivers/block/ublk_drv.c:1776
 ublk_cmd_tw_cb+0xbe/0x110 drivers/block/ublk_drv.c:2067
 tctx_task_work_run+0xabe/0xbf0 io_uring/tw.c:96
 tctx_task_work+0x7a/0xa0 io_uring/tw.c:133
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x8da/0x2a50 kernel/exit.c:986
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1129
 __do_sys_exit_group kernel/exit.c:1140 [inline]
 __se_sys_exit_group kernel/exit.c:1138 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1138
 x64_sys_call+0x1567/0x1570 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f666519e199
Code: Unable to access opcode bytes at 0x7f666519e16f.
RSP: 002b:00007ffd49c32568 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f666519e199
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 0000000000000000 R09: 00007f66653ed3e0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f66653ed3e0 R14: 0000000000000003 R15: 00007ffd49c32620
 </TASK>
I/O error, dev ublkb0, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2
Buffer I/O error on dev ublkb0, logical block 0, async page read