=============================
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-executor388/5630: 1, last CPU#0:
 #0: ffff888029fc40a0 (&ctx->uring_lock){+.+.}-{4:4}, at: tctx_task_work_run+0x2d3/0xa80 io_uring/tw.c:92

stack backtrace:
CPU: 0 UID: 0 PID: 5630 Comm: syz-executor388 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 lockdep_rcu_suspicious+0x140/0x1d0 kernel/locking/lockdep.c:6972
 mas_root lib/maple_tree.c:720 [inline]
 mas_start+0x3cc/0x640 lib/maple_tree.c:1250
 mas_state_walk lib/maple_tree.c:3006 [inline]
 mas_walk+0x1db/0x490 lib/maple_tree.c:4458
 ublk_try_buf_match drivers/block/ublk_drv.c:5639 [inline]
 ublk_init_iod+0x5d2/0x1120 drivers/block/ublk_drv.c:521
 ublk_dispatch_req+0x97/0x9c0 drivers/block/ublk_drv.c:1776
 tctx_task_work_run+0x73d/0xa80 io_uring/tw.c:96
 tctx_task_work+0x3f/0x60 io_uring/tw.c:133
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x73a/0x2360 kernel/exit.c:1011
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1154
 __do_sys_exit_group kernel/exit.c:1165 [inline]
 __se_sys_exit_group kernel/exit.c:1163 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1163
 x64_sys_call+0x18c6/0x18d0 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdd4b52c325
Code: Unable to access opcode bytes at 0x7fdd4b52c2fb.
RSP: 002b:00007ffd716ddcc8 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fdd4b52c325
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fdd4b5c5158 R14: 00007fdd4b5c7408 R15: 00007fdd4b5c7420
 </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
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