=============================
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.0.17/4934: 1, last CPU#1:
 #0: ffff0000d0bf20a0 (&ctx->uring_lock){+.+.}-{4:4}, at: tctx_task_work_run+0x288/0xc2c io_uring/tw.c:92

stack backtrace:
CPU: 1 UID: 0 PID: 4934 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 dump_stack+0x1c/0x28 lib/dump_stack.c:129
 lockdep_rcu_suspicious+0x168/0x26c kernel/locking/lockdep.c:6938
 mas_root lib/maple_tree.c:720 [inline]
 mas_start+0x3a0/0x5b4 lib/maple_tree.c:1250
 mas_state_walk lib/maple_tree.c:3006 [inline]
 mas_walk+0x9c/0x2b8 lib/maple_tree.c:4458
 ublk_try_buf_match drivers/block/ublk_drv.c:5632 [inline]
 ublk_init_iod+0x4a4/0xa68 drivers/block/ublk_drv.c:521
 ublk_setup_iod+0x1e8/0x260 drivers/block/ublk_drv.c:-1
 ublk_dispatch_req+0x94/0x52c drivers/block/ublk_drv.c:1776
 ublk_cmd_tw_cb+0x64/0x78 drivers/block/ublk_drv.c:2067
 tctx_task_work_run+0x5bc/0xc2c io_uring/tw.c:96
 tctx_task_work+0x3c/0x68 io_uring/tw.c:133
 task_work_run+0x1cc/0x25c kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x58c/0x1a74 kernel/exit.c:1008
 do_group_exit+0x198/0x238 kernel/exit.c:1151
 __do_sys_exit_group kernel/exit.c:1162 [inline]
 __se_sys_exit_group kernel/exit.c:1160 [inline]
 pid_child_should_wake+0x0/0x104 kernel/exit.c:1160
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
 el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590
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