syzbot

INFO: task syz.3.4738:12782 blocked for more than 122 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.4738      state:D stack:0     pid:12782 tgid:12781 ppid:9482   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5996 [inline]
 __schedule+0x134f/0x1ea0 kernel/sched/core.c:7843
 __schedule_loop kernel/sched/core.c:7924 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7939
 schedule_preempt_disabled+0x14/0x30 kernel/sched/core.c:7996
 __mutex_lock_common kernel/locking/mutex.c:707 [inline]
 __mutex_lock+0x960/0x1bb0 kernel/locking/mutex.c:803
 __mutex_lock_slowpath+0xe/0x20 kernel/locking/mutex.c:1134
 mutex_lock+0x113/0x1d0 kernel/locking/mutex.c:285
 loop_reread_partitions+0x4a/0x110 drivers/block/loop.c:466
 loop_configure+0x1068/0x13a0 drivers/block/loop.c:1078
 lo_ioctl+0xa8b/0x2070 drivers/block/loop.c:1520
 blkdev_ioctl+0x54b/0x690 block/ioctl.c:699
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0x135/0x1b0 fs/ioctl.c:893
 __x64_sys_ioctl+0x7f/0xa0 fs/ioctl.c:893
 x64_sys_call+0x1878/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f815cb9c629
RSP: 002b:00007f815da92028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f815ce15fa0 RCX: 00007f815cb9c629
RDX: 0000200000000080 RSI: 0000000000004c0a RDI: 0000000000000005
RBP: 00007f815cc32b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f815ce16038 R14: 00007f815ce15fa0 R15: 00007fff133f7198
 </TASK>
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 d51130501c30ee86aaec4f48ba6958e62aa015e3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 dump_stack+0x19/0x20 lib/dump_stack.c:129
 nmi_cpu_backtrace+0x2ba/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x142/0x2c0 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:41
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:267 [inline]
 watchdog+0xdad/0xf00 kernel/hung_task.c:423
 kthread+0x2c9/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 d51130501c30ee86aaec4f48ba6958e62aa015e3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:handle_softirqs+0x7e/0x630 kernel/softirq.c:590
Code: 28 2d b4 7e 49 8d 5f 2c 48 89 d8 48 c1 e8 03 48 89 45 a0 0f b6 04 08 84 c0 0f 85 40 05 00 00 48 89 5d 98 41 8b 47 2c 89 45 bc <25> ff f7 ff ff 41 89 47 2c 65 66 8b 05 19 2d b4 7e 44 0f b7 f0 49
RSP: 0018:ffffc90000230f38 EFLAGS: 00000046
RAX: 0000000004200042 RBX: ffff88810366df2c RCX: dffffc0000000000
RDX: 0000000000010000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000230fc0 R08: ffff8881f6f4fa07 R09: 1ffff1103ede9f40
R10: dffffc0000000000 R11: ffffed103ede9f41 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: ffff88810366df00
FS:  0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5ba7be82f8 CR3: 0000000109264000 CR4: 00000000003526b0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000083
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __do_softirq kernel/softirq.c:659 [inline]
 invoke_softirq kernel/softirq.c:476 [inline]
 __irq_exit_rcu+0x47/0xb0 kernel/softirq.c:708
 irq_exit_rcu+0xd/0x30 kernel/softirq.c:720
 instr_sysvec_call_function_single arch/x86/kernel/smp.c:266 [inline]
 sysvec_call_function_single+0x7f/0x90 arch/x86/kernel/smp.c:266
 </IRQ>
 <TASK>
 asm_sysvec_call_function_single+0x1f/0x30 arch/x86/include/asm/idtentry.h:709
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:106
Code: cc cc cc cc cc cc cc b8 d5 ec dd ec 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d d3 7c 48 00 55 48 89 e5 fb f4 <5d> c3 cc cc cc cc cc cc cc cc cc cc cc b8 00 00 00 00 90 90 90 90
RSP: 0018:ffffc900001a7e00 EFLAGS: 000002c2
RAX: ffff8881f6f00000 RBX: ffff88810366df00 RCX: ffffffff859eda4d
RDX: 0000000000000001 RSI: 0000000000000004 RDI: 0000000001111ac4
RBP: ffffc900001a7e00 R08: ffff8881f6f39733 R09: 1ffff1103ede72e6
R10: dffffc0000000000 R11: ffffed103ede72e7 R12: 1ffff110206cdbe0
R13: 0000000000000001 R14: 0000000000000000 R15: ffffffff87ebd068
 arch_safe_halt arch/x86/include/asm/paravirt.h:112 [inline]
 default_idle+0x17/0x30 arch/x86/kernel/process.c:754
 arch_cpu_idle+0xd/0x20 arch/x86/kernel/process.c:791
 default_idle_call+0x3e/0x80 kernel/sched/idle.c:117
 cpuidle_idle_call kernel/sched/idle.c:185 [inline]
 do_idle+0x19f/0x4b0 kernel/sched/idle.c:326
 cpu_startup_entry+0x47/0x60 kernel/sched/idle.c:424
 start_secondary+0x12e/0x140 arch/x86/kernel/smpboot.c:314
 common_startup_64+0x13b/0x157
 </TASK>