syzbot


INFO: task hung in userfaultfd_release_all (2)

Status: auto-obsoleted due to no activity on 2026/05/13 11:09
Subsystems: mm
[Documentation on labels]
First crash: 113d, last: 113d
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in userfaultfd_release_all mm 1 12 340d 352d 0/29 auto-obsoleted due to no activity on 2025/09/18 11:45

Sample crash report:
INFO: task syz.5.1162:9241 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.1162      state:D stack:23520 pid:9241  tgid:9241  ppid:7402   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5352 [inline]
 __schedule+0x1665/0x5590 kernel/sched/core.c:6964
 __schedule_loop kernel/sched/core.c:7047 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7062
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7119
 rwsem_down_write_slowpath+0x883/0x1080 kernel/locking/rwsem.c:1215
 __down_write_common kernel/locking/rwsem.c:1347 [inline]
 __down_write kernel/locking/rwsem.c:1356 [inline]
 down_write+0x1bc/0x200 kernel/locking/rwsem.c:1626
 mmap_write_lock include/linux/mmap_lock.h:536 [inline]
 userfaultfd_release_all+0x178/0x610 mm/userfaultfd.c:2217
 userfaultfd_release+0xef/0x1c0 fs/userfaultfd.c:887
 __fput+0x44f/0xa70 fs/file_table.c:469
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:269 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4351d9c799
RSP: 002b:00007ffd5ce9d448 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f4352017da0 RCX: 00007f4351d9c799
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f4352017da0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007f4352017cb0 R11: 0000000000000246 R12: 0000000000042551
R13: 00007f435201627c R14: 0000000000042457 R15: 00007f4352016270
 </TASK>
INFO: task syz.5.1162:9248 blocked for more than 144 seconds.
      Not tainted syzkaller #0
      Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.1162      state:D stack:28064 pid:9248  tgid:9241  ppid:7402   task_flags:0x40054c flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5352 [inline]
 __schedule+0x1665/0x5590 kernel/sched/core.c:6964
 __schedule_loop kernel/sched/core.c:7047 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7062
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7119
 rwsem_down_read_slowpath+0x6d9/0x940 kernel/locking/rwsem.c:1114
 __down_read_common kernel/locking/rwsem.c:1291 [inline]
 __down_read kernel/locking/rwsem.c:1304 [inline]
 down_read+0x99/0x2e0 kernel/locking/rwsem.c:1570
 mmap_read_lock include/linux/mmap_lock.h:592 [inline]
 exit_mm+0x73/0x250 kernel/exit.c:557
 do_exit+0x8b9/0x2490 kernel/exit.c:962
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1116
 get_signal+0x1284/0x1330 kernel/signal.c:3035
 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:269 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4351d9c799
RSP: 002b:00007f4352c620e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f4352016278 RCX: 00007f4351d9c799
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f4352016278
RBP: 00007f4352016270 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4352016308 R14: 00007ffd5ce9d200 R15: 00007ffd5ce9d2e8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/30:
 #0: ffffffff8e75d6a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #0: ffffffff8e75d6a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #0: ffffffff8e75d6a0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
2 locks held by getty/5591:
 #0: ffff888032d7e0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000332b2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45c/0x13c0 drivers/tty/n_tty.c:2211
3 locks held by kworker/0:5/5918:
1 lock held by syz.5.1162/9241:
 #0: ffff88807dd7b538 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock include/linux/mmap_lock.h:536 [inline]
 #0: ffff88807dd7b538 (&mm->mmap_lock){++++}-{4:4}, at: userfaultfd_release_all+0x178/0x610 mm/userfaultfd.c:2217
1 lock held by syz.5.1162/9248:
 #0: ffff88807dd7b538 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock include/linux/mmap_lock.h:592 [inline]
 #0: ffff88807dd7b538 (&mm->mmap_lock){++++}-{4:4}, at: exit_mm+0x73/0x250 kernel/exit.c:557
2 locks held by syz.3.2276/12234:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0x1002/0x1060 kernel/hung_task.c:561
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 12234 Comm: syz.3.2276 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:arch_stack_walk+0xf3/0x150 arch/x86/kernel/stacktrace.c:26
Code: 78 ff ff ff 00 00 00 00 48 8d bd 78 ff ff ff 4c 89 e6 4c 89 fa e8 ed 9c 09 00 83 bd 78 ff ff ff 00 74 38 4c 8d bd 78 ff ff ff <4c> 89 ff e8 e5 72 09 00 48 85 c0 74 24 48 89 df 48 89 c6 4d 89 f3
RSP: 0018:ffffc90005c9e5a8 EFLAGS: 00000202
RAX: 0000000091349901 RBX: ffffc90005c9e660 RCX: 0000000000000046
RDX: 0000000000000001 RSI: ffffffff8e18595e RDI: ffff8880269e3d00
RBP: ffffc90005c9e630 R08: ffffc90005c9ec88 R09: 0000000000000000
R10: ffffc90005c9e5f8 R11: fffff52000b93cc1 R12: ffff8880269e3d00
R13: 0000000000000000 R14: ffffffff81b1cb00 R15: ffffc90005c9e5a8
FS:  00007f7161f9e6c0(0000) GS:ffff888125536000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3160dff8 CR3: 0000000033672000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2689 [inline]
 slab_free mm/slub.c:6242 [inline]
 kfree+0x1c5/0x650 mm/slub.c:6557
 hash_ip4_ahash_destroy net/netfilter/ipset/ip_set_hash_gen.h:441 [inline]
 hash_ip4_resize+0x1780/0x1a20 net/netfilter/ipset/ip_set_hash_gen.h:781
 call_ad+0x463/0xb60 net/netfilter/ipset/ip_set_core.c:1757
 ip_set_ad+0x824/0x9d0 net/netfilter/ipset/ip_set_core.c:1841
 nfnetlink_rcv_msg+0xc03/0x12c0 net/netfilter/nfnetlink.c:300
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
 nfnetlink_rcv+0x2c0/0x27b0 net/netfilter/nfnetlink.c:667
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec+0x112/0x150 net/socket.c:796
 __sock_sendmsg net/socket.c:811 [inline]
 ____sys_sendmsg+0x589/0x8c0 net/socket.c:2668
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2722
 __sys_sendmsg net/socket.c:2754 [inline]
 __do_sys_sendmsg net/socket.c:2759 [inline]
 __se_sys_sendmsg net/socket.c:2757 [inline]
 __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2757
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f716119c799
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:00007f7161f9e028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f7161415fa0 RCX: 00007f716119c799
RDX: 0000000004000084 RSI: 0000200000000000 RDI: 0000000000000008
RBP: 00007f7161232c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7161416038 R14: 00007f7161415fa0 R15: 00007ffe3fcde2f8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/14 11:04 linux-next b84a0ebe421c ee8d34d6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: task hung in userfaultfd_release_all
* Struck through repros no longer work on HEAD.