[syzbot] [block?] WARNING: suspicious RCU usage in mas_start (2)

[syzbot <syzbot+b48868c46e62c1c4cb2c@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    704340f1cd0d Merge tag 'x86_urgent_for_7.3-rc4' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16091925580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5c3949d762a91f
dashboard link: https://syzkaller.appspot.com/bug?extid=b48868c46e62c1c4cb2c
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=120f305e580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=117fb5f9580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-704340f1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e02afc1c5927/vmlinux-704340f1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/09cb4a8b3309/bzImage-704340f1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b48868c46e62c1c4cb2c@syzkaller.appspotmail.com

=============================
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.0.17/5926: 1, last CPU#0:
 #0: ffff888034a420a0 (&ctx->uring_lock){+.+.}-{4:4}, at: tctx_task_work_run+0x1cd/0xbf0 io_uring/tw.c:92

stack backtrace:
CPU: 0 UID: 0 PID: 5926 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+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]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1163
 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: 0033:0x7f35df99e159
Code: Unable to access opcode bytes at 0x7f35df99e12f.
RSP: 002b:00007ffcaa2c82b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f35df99e159
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 0000000000000000 R09: 00007f35dfbec3e0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f35dfbec3e0 R14: 0000000000000003 R15: 00007ffcaa2c8370
 </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


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