=============================
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.0.17/5928: 1, last CPU#2:
 #0: ffff888026a600a0 (&ctx->uring_lock){+.+.}-{4:4}, at: tctx_task_work_run+0x1cd/0xbf0 io_uring/tw.c:92

stack backtrace:
CPU: 2 UID: 0 PID: 5928 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:5638
 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+0x951/0x2ae0 kernel/exit.c:1011
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1154
 __do_sys_exit_group kernel/exit.c:1165 [inline]
 __se_sys_exit_group kernel/exit.c:1163 [inline]
 __ia32_sys_exit_group+0x3e/0x50 kernel/exit.c:1163
 ia32_sys_call+0x1a39/0x1a40 arch/x86/include/generated/asm/syscalls_32.h:253
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
 __do_fast_syscall_32+0x13a/0x8b0 arch/x86/entry/syscall_32.c:291
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:316
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf705efec
Code: Unable to access opcode bytes at 0xf705efc2.
RSP: 002b:00000000ffc7d7fc EFLAGS: 00000286 ORIG_RAX: 00000000000000fc
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 00000000ffffff9c RDI: 00000000f71c8699
RBP: 00000000f7428ff4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </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