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INFO: rcu detected stall in __tun_chr_ioctl

Status: auto-obsoleted due to no activity on 2026/03/26 13:49
Reported-by: syzbot+9880bfcee0c54e33bf3b@syzkaller.appspotmail.com
First crash: 126d, last: 102d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in __tun_chr_ioctl mm 1 4 435d 510d 0/29 auto-obsoleted due to no activity on 2025/04/18 05:25
linux-5.15 INFO: rcu detected stall in __tun_chr_ioctl 1 1 387d 387d 0/3 auto-obsoleted due to no activity on 2025/06/14 12:09
linux-6.6 INFO: rcu detected stall in __tun_chr_ioctl 1 1 6d10h 6d10h 0/2 upstream: reported on 2026/03/23 00:03
linux-6.1 INFO: rcu detected stall in __tun_chr_ioctl (2) 1 1 15h55m 15h55m 0/3 upstream: reported on 2026/03/28 18:58
linux-5.15 INFO: rcu detected stall in __tun_chr_ioctl (2) 1 8 25d 125d 0/3 upstream: reported on 2025/11/23 13:35

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2650 jiffies s: 321661 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 31254 Comm: syz.3.7117 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:native_apic_msr_eoi_write+0xb/0x10 arch/x86/include/asm/apic.h:212
Code: 8b 06 bf f0 03 00 00 89 de 5b 41 5e 41 5f ff e0 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b9 0b 08 00 00 31 c0 31 d2 0f 30 <c3> 0f 1f 40 00 81 ff cf 00 00 00 7f 0c 83 ff 20 74 2a 83 ff 30 74
RSP: 0018:ffffc900001e09b8 EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffffffff8c3d8b30 RCX: 000000000000080b
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000000000b0
RBP: 0000000000000000 R08: ffffffff8f7dd048 R09: ffffffff8f7dd058
R10: ffffffff8f7dd050 R11: ffffffff8f7dd043 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
FS:  00007f586e70b6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000034000 CR3: 00000000857b8000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 apic_eoi arch/x86/include/asm/apic.h:399 [inline]
 ack_APIC_irq arch/x86/include/asm/apic.h:445 [inline]
 __sysvec_irq_work+0x53/0x350 arch/x86/kernel/irq_work.c:19
 instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
 sysvec_irq_work+0x4a/0xc0 arch/x86/kernel/irq_work.c:17
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x84/0x500 kernel/rcu/tree_plugin.h:685
Code: f1 f1 f1 00 f2 f2 f2 4a 89 04 2b 66 42 c7 44 2b 09 f3 f3 42 c6 44 2b 0b f3 65 44 8b 35 fd 86 96 7e 41 f7 c6 00 00 f0 00 74 45 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 66 42 c7 44 2b
RSP: 0018:ffffc900001e0aa0 EFLAGS: 00000206
RAX: d51357956d582b00 RBX: 1ffff9200003c15c RCX: d51357956d582b00
RDX: dffffc0000000000 RSI: ffffffff8a6c0600 RDI: ffffffff8abef920
RBP: ffffc900001e0b90 R08: dffffc0000000000 R09: fffffbfff211904a
R10: fffffbfff211904a R11: 1ffffffff2119049 R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3b900 R15: 0000000000000002
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
 mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2147
 __run_hrtimer kernel/time/hrtimer.c:1747 [inline]
 __hrtimer_run_queues+0x554/0xd60 kernel/time/hrtimer.c:1811
 hrtimer_run_softirq+0x183/0x2a0 kernel/time/hrtimer.c:1828
 handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
 __do_softirq kernel/softirq.c:630 [inline]
 invoke_softirq kernel/softirq.c:470 [inline]
 __irq_exit_rcu+0x12f/0x220 kernel/softirq.c:679
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:_compound_head include/linux/page-flags.h:255 [inline]
RIP: 0010:virt_to_folio include/linux/mm.h:915 [inline]
RIP: 0010:virt_to_slab mm/slab.h:175 [inline]
RIP: 0010:qlink_to_cache+0x1c/0xa0 mm/kasan/quarantine.c:131
Code: 83 c4 20 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 db 35 68 ff 48 c1 e8 06 48 83 e0 c0 48 ba 00 00 00 00 00 ea ff ff 48 8b 4c 10 08 <f6> c1 01 75 76 48 01 d0 66 90 48 8b 48 08 f6 c1 01 75 3e 66 90 48
RSP: 0018:ffffc9000d71f508 EFLAGS: 00000202
RAX: 00000000009b0780 RBX: ffffc9000d71f550 RCX: ffffea00009b0601
RDX: ffffea0000000000 RSI: 0000000000046018 RDI: 0000000000046019
RBP: ffff888026c1e000 R08: ffff888053169640 R09: 00000000800c0003
R10: fffffbfff211904a R11: 1ffffffff2119049 R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff888026c1e000
 qlist_free_all+0x3a/0xe0 mm/kasan/quarantine.c:184
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x480 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 slab_alloc mm/slub.c:3367 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3374 [inline]
 kmem_cache_alloc+0x123/0x2f0 mm/slub.c:3383
 kmem_cache_zalloc include/linux/slab.h:689 [inline]
 __kernfs_new_node+0xd4/0x7d0 fs/kernfs/dir.c:614
 kernfs_new_node+0x148/0x250 fs/kernfs/dir.c:690
 __kernfs_create_file+0x47/0x2e0 fs/kernfs/file.c:1068
 sysfs_add_file_mode_ns+0x234/0x2f0 fs/sysfs/file.c:294
 create_files fs/sysfs/group.c:64 [inline]
 internal_create_group+0x487/0xce0 fs/sysfs/group.c:148
 internal_create_groups fs/sysfs/group.c:188 [inline]
 sysfs_create_groups+0x55/0x120 fs/sysfs/group.c:214
 device_add_groups drivers/base/core.c:2752 [inline]
 device_add_attrs+0x1ae/0x800 drivers/base/core.c:2911
 device_add+0x64b/0xfb0 drivers/base/core.c:3648
 netdev_register_kobject+0x176/0x310 net/core/net-sysfs.c:2013
 register_netdevice+0x12b9/0x1aa0 net/core/dev.c:10204
 tun_set_iff+0x848/0xed0 drivers/net/tun.c:2851
 __tun_chr_ioctl+0x730/0x1e10 drivers/net/tun.c:3114
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f586d78f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f586e70b038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f586d9e5fa0 RCX: 00007f586d78f749
RDX: 0000200000000080 RSI: 00000000400454ca RDI: 000000000000000b
RBP: 00007f586d813f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f586d9e6038 R14: 00007f586d9e5fa0 R15: 00007fff28d47f58
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/16 13:49 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2025/12/04 06:29 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
2025/11/22 11:38 linux-6.1.y f6e38ae624cf 4fb8ef37 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __tun_chr_ioctl
* Struck through repros no longer work on HEAD.