syzbot


INFO: task hung in kvm_swap_active_memslots (2)

Status: upstream: reported on 2025/11/17 10:44
Subsystems: kvm
[Documentation on labels]
Reported-by: syzbot+5c566b850d6ab6f0427a@syzkaller.appspotmail.com
First crash: 53d, last: 7d13h
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [kvm?] INFO: task hung in kvm_swap_active_memslots (2) 2 (3) 2025/11/17 16:54
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in kvm_swap_active_memslots kvm 1 3 247d 305d 0/29 auto-obsoleted due to no activity on 2025/07/02 12:01

Sample crash report:
INFO: task syz.4.4903:29412 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.4903      state:D stack:25000 pid:29412 tgid:29408 ppid:27154  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:7026
 kvm_swap_active_memslots+0x2ea/0x7d0 virt/kvm/kvm_main.c:1642
 kvm_activate_memslot virt/kvm/kvm_main.c:1786 [inline]
 kvm_create_memslot virt/kvm/kvm_main.c:1852 [inline]
 kvm_set_memslot+0xd3b/0x1380 virt/kvm/kvm_main.c:1964
 kvm_set_memory_region+0xe53/0x1610 virt/kvm/kvm_main.c:2120
 kvm_set_internal_memslot+0x9f/0xe0 virt/kvm/kvm_main.c:2143
 __x86_set_memory_region+0x2f6/0x740 arch/x86/kvm/x86.c:13252
 kvm_alloc_apic_access_page+0xc5/0x140 arch/x86/kvm/lapic.c:2788
 vmx_vcpu_create+0x503/0xbd0 arch/x86/kvm/vmx/vmx.c:7607
 kvm_arch_vcpu_create+0x688/0xb20 arch/x86/kvm/x86.c:12705
 kvm_vm_ioctl_create_vcpu virt/kvm/kvm_main.c:4207 [inline]
 kvm_vm_ioctl+0xfec/0x3fd0 virt/kvm/kvm_main.c:5158
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb73f38f7c9
RSP: 002b:00007fb7402ea038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fb73f5e5fa0 RCX: 00007fb73f38f7c9
RDX: 0000000000000000 RSI: 000000000000ae41 RDI: 0000000000000003
RBP: 00007fb73f413f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb73f5e6038 R14: 00007fb73f5e5fa0 R15: 00007ffd3863a848
 </TASK>

Showing all locks held in the system:
1 lock held by pool_workqueue_/3:
 #0: ffffffff8e3cfb78 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x1a3/0x3c0 kernel/rcu/tree_exp.h:343
1 lock held by khungtaskd/31:
 #0: ffffffff8e3c45e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e3c45e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #0: ffffffff8e3c45e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6775
2 locks held by khugepaged/38:
3 locks held by kworker/u10:3/21774:
 #0: ffff88801ba9f148 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc90003057d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
 #2: ffffffff900d5090 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xad/0x8b0 net/core/net_namespace.c:669
1 lock held by syz.0.4407/26887:
2 locks held by syz.4.4903/29412:
 #0: ffff888146be00a8 (&kvm->slots_lock){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:228 [inline]
 #0: ffff888146be00a8 (&kvm->slots_lock){+.+.}-{4:4}, at: kvm_alloc_apic_access_page+0x27/0x140 arch/x86/kvm/lapic.c:2782
 #1: ffff888146be0138 (&kvm->slots_arch_lock){+.+.}-{4:4}, at: kvm_set_memslot+0x34/0x1380 virt/kvm/kvm_main.c:1915
2 locks held by getty/31846:
 #0: ffff8880341840a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000bacb2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x14f0 drivers/tty/n_tty.c:2222
2 locks held by syz.6.5436/31950:
 #0: ffffffff900d5090 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x2d6/0x690 net/core/net_namespace.c:576
 #1: ffffffff8e3cfb78 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x1a3/0x3c0 kernel/rcu/tree_exp.h:343
1 lock held by syz.2.5442/31973:
 #0: ffff88805d5e2488 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:980 [inline]
 #0: ffff88805d5e2488 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: __sock_release+0x86/0x270 net/socket.c:661

=============================================

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:332 [inline]
 watchdog+0xf3f/0x1170 kernel/hung_task.c:495
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/29 01:25 upstream e538109ac71d d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in kvm_swap_active_memslots
2025/11/28 19:51 upstream e538109ac71d d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in kvm_swap_active_memslots
2025/11/19 13:20 upstream 8b690556d8fe 82d7b894 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in kvm_swap_active_memslots
2025/11/18 03:20 upstream e7c375b18160 ef766cd7 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in kvm_swap_active_memslots
2025/10/14 04:02 upstream 3a8660878839 b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in kvm_swap_active_memslots
* Struck through repros no longer work on HEAD.