syzbot

INFO: task syz-executor:289 blocked for more than 122 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:0     pid:289   tgid:289   ppid:1      flags:0x00000004
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
 rwsem_down_write_slowpath+0x5b0/0x1bb0 kernel/locking/rwsem.c:1239
 __down_write_common kernel/locking/rwsem.c:1383 [inline]
 __down_write kernel/locking/rwsem.c:1392 [inline]
 down_write+0x163/0x2b0 kernel/locking/rwsem.c:1659
 namespace_lock fs/namespace.c:1720 [inline]
 do_umount fs/namespace.c:1912 [inline]
 path_umount+0x870/0xf50 fs/namespace.c:2020
 ksys_umount fs/namespace.c:2043 [inline]
 __do_sys_umount fs/namespace.c:2048 [inline]
 __se_sys_umount fs/namespace.c:2046 [inline]
 __x64_sys_umount+0x12e/0x180 fs/namespace.c:2046
 x64_sys_call+0x2ab8/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:167
 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: 0033:0x7fb5ac59d1d7
RSP: 002b:00007fff2c9e4998 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: ffffffffffffffda RBX: 00007fb5ac631c3b RCX: 00007fb5ac59d1d7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007fff2c9e4a50
RBP: 00007fff2c9e4a50 R08: 00007fff2c9e5a50 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff2c9e5ae0
R13: 00007fb5ac631c3b R14: 000000000000e682 R15: 00007fff2c9e5b20
 </TASK>
INFO: task syz.3.173:892 blocked for more than 124 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.173       state:D stack:0     pid:892   tgid:890   ppid:292    flags:0x00000004
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
 rwsem_down_write_slowpath+0x5b0/0x1bb0 kernel/locking/rwsem.c:1239
 __down_write_common kernel/locking/rwsem.c:1383 [inline]
 __down_write kernel/locking/rwsem.c:1392 [inline]
 down_write+0x163/0x2b0 kernel/locking/rwsem.c:1659
 inode_lock include/linux/fs.h:817 [inline]
 do_lock_mount+0x218/0x540 fs/namespace.c:2638
 lock_mount fs/namespace.c:2683 [inline]
 do_loopback+0x25d/0x4c0 fs/namespace.c:2820
 path_mount+0x56b/0x1010 fs/namespace.c:3878
 do_mount fs/namespace.c:3897 [inline]
 __do_sys_mount fs/namespace.c:4107 [inline]
 __se_sys_mount+0x2bf/0x480 fs/namespace.c:4084
 __x64_sys_mount+0xc3/0xf0 fs/namespace.c:4084
 x64_sys_call+0x2021/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:166
 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: 0033:0x7f7bd7b9bf79
RSP: 002b:00007f7bd8af1028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f7bd7e16090 RCX: 00007f7bd7b9bf79
RDX: 0000000000000000 RSI: 0000200000000300 RDI: 0000200000000100
RBP: 00007f7bd7c327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000002151090 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7bd7e16128 R14: 00007f7bd7e16090 R15: 00007ffe3c4c4588
 </TASK>
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 eb3ac94483332de1dcdde2e475b5ff9bbded7b99
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 891 Comm: syz.3.173 Not tainted syzkaller #0 eb3ac94483332de1dcdde2e475b5ff9bbded7b99
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:do_make_slave fs/pnode.c:101 [inline]
RIP: 0010:change_mnt_propagation+0xff/0xb00 fs/pnode.c:128
Code: 11 e7 ff 4d 8b 2e 48 c7 c3 28 ff ff ff 4d 89 fc 4d 8d 74 24 20 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 <74> 08 4c 89 f7 e8 17 11 e7 ff 4d 39 2e 0f 84 8f 00 00 00 49 81 c4
RSP: 0018:ffffc9000fb579c0 EFLAGS: 00000246
RAX: 1ffff11027a35f14 RBX: ffffffffffffff28 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000040000 RDI: 0000000000100000
RBP: ffffc9000fb57a10 R08: ffff88811422a4af R09: 0000000000000000
R10: ffff88811422a4a0 R11: ffffed1022845496 R12: ffff88813d1af880
R13: ffff8881117b7440 R14: ffff88813d1af8a0 R15: ffff8881396601c0
FS:  00007f7bd8b126c0(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f88f056ffa8 CR3: 00000001144e6000 CR4: 00000000003526b0
Call Trace:
 <TASK>
 umount_tree+0xe16/0xf90 fs/namespace.c:1813
 attach_recursive_mnt+0x6e7/0x2210 fs/namespace.c:2569
 graft_tree+0x157/0x1c0 fs/namespace.c:2704
 do_loopback+0x36a/0x4c0 fs/namespace.c:2836
 path_mount+0x56b/0x1010 fs/namespace.c:3878
 do_mount fs/namespace.c:3897 [inline]
 __do_sys_mount fs/namespace.c:4107 [inline]
 __se_sys_mount+0x2bf/0x480 fs/namespace.c:4084
 __x64_sys_mount+0xc3/0xf0 fs/namespace.c:4084
 x64_sys_call+0x2021/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:166
 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: 0033:0x7f7bd7b9bf79
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7bd8b12028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f7bd7e15fa0 RCX: 00007f7bd7b9bf79
RDX: 0000000000000000 RSI: 0000200000000300 RDI: 0000200000000100
RBP: 00007f7bd7c327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000002151090 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7bd7e16038 R14: 00007f7bd7e15fa0 R15: 00007ffe3c4c4588
 </TASK>