* [syzbot] [mm?] INFO: rcu detected stall in kcov_ioctl (3)
@ 2026-04-08 23:31 syzbot
2026-04-08 23:52 ` Andrew Morton
0 siblings, 1 reply; 2+ messages in thread
From: syzbot @ 2026-04-08 23:31 UTC (permalink / raw)
To: akpm, hannes, jackmanb, linux-kernel, linux-mm, mhocko, surenb,
syzkaller-bugs, vbabka, ziy
Hello,
syzbot found the following issue on:
HEAD commit: 7ca6d1cfec80 Merge tag 'powerpc-7.0-4' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=133b4dda580000
kernel config: https://syzkaller.appspot.com/x/.config?x=64e78d99d9bf8b4c
dashboard link: https://syzkaller.appspot.com/bug?extid=8a59070fc852219166ab
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ace9641c44ac/disk-7ca6d1cf.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6e66f8b9476e/vmlinux-7ca6d1cf.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d679c066df56/bzImage-7ca6d1cf.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8a59070fc852219166ab@syzkaller.appspotmail.com
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P23414/1:b..l P27649/1:b..l P27664/1:b..l
rcu: (detected by 0, t=10502 jiffies, g=200461, q=440 ncpus=2)
task:syz-executor state:R running task stack:25416 pid:27664 tgid:27664 ppid:5809 task_flags:0x400000 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5298 [inline]
__schedule+0xfee/0x6120 kernel/sched/core.c:6911
preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7238
irqentry_exit+0x17b/0x670 kernel/entry/common.c:239
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__orc_find+0x49/0xf0 arch/x86/kernel/unwind_orc.c:101
Code: 00 49 89 fe 48 89 f0 49 39 fc 72 7b 48 b9 00 00 00 00 00 fc ff df 49 89 ff 48 89 fd eb 0c 48 8d 6b 04 49 89 df 49 39 ec 72 4e <4c> 89 e2 48 29 ea 48 89 d6 48 c1 ea 3f 48 c1 fe 02 48 01 f2 48 d1
RSP: 0018:ffffc9000d12f138 EFLAGS: 00000212
RAX: ffffffff91777f46 RBX: ffffffff90f165c4 RCX: dffffc0000000000
RDX: ffffffff81aecd9f RSI: 0000000000000000 RDI: ffffffff90f165b8
RBP: ffffffff90f165b8 R08: ffffffff91777f70 R09: 0000000000000007
R10: 0000000000000200 R11: 000000000000aecd R12: ffffffff90f165c0
R13: ffffffff81aecd22 R14: ffffffff90f165b8 R15: ffffffff90f165b8
orc_find arch/x86/kernel/unwind_orc.c:238 [inline]
unwind_next_frame+0x2ec/0x1ea0 arch/x86/kernel/unwind_orc.c:510
__unwind_start+0x3d1/0x7f0 arch/x86/kernel/unwind_orc.c:773
unwind_start arch/x86/include/asm/unwind.h:64 [inline]
arch_stack_walk+0x73/0xf0 arch/x86/kernel/stacktrace.c:24
stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
save_stack+0x162/0x1e0 mm/page_owner.c:165
__set_page_owner+0x8c/0x540 mm/page_owner.c:341
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x153/0x170 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x111d/0x3140 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x27c/0x2ba0 mm/page_alloc.c:5250
__alloc_pages_noprof mm/page_alloc.c:5284 [inline]
alloc_pages_bulk_noprof+0x782/0x1490 mm/page_alloc.c:5204
___alloc_pages_bulk mm/kasan/shadow.c:345 [inline]
__kasan_populate_vmalloc_do mm/kasan/shadow.c:370 [inline]
__kasan_populate_vmalloc+0xf0/0x210 mm/kasan/shadow.c:424
kasan_populate_vmalloc include/linux/kasan.h:580 [inline]
alloc_vmap_area+0x95d/0x2bd0 mm/vmalloc.c:2129
__get_vm_area_node+0x1ca/0x330 mm/vmalloc.c:3232
__vmalloc_node_range_noprof+0x213/0x1530 mm/vmalloc.c:4024
vmalloc_user_noprof+0x9e/0xe0 mm/vmalloc.c:4218
kcov_ioctl+0x4c/0x720 kernel/kcov.c:726
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+0x106/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb4e519c4ab
RSP: 002b:00007fff4cf1e620 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000100000 RCX: 00007fb4e519c4ab
RDX: 0000000000100000 RSI: ffffffff80086301 RDI: 00000000000000d7
RBP: 00007fb4e5415f40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000003 R14: 00007fff4cf1e8d8 R15: 0000000000000000
</TASK>
task:syz.0.5971 state:R running task stack:26536 pid:27649 tgid:27649 ppid:23762 task_flags:0x40044c flags:0x00080003
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5298 [inline]
__schedule+0xfee/0x6120 kernel/sched/core.c:6911
preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7238
irqentry_exit+0x17b/0x670 kernel/entry/common.c:239
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_acquire+0x5e/0x380 kernel/locking/lockdep.c:5872
Code: 05 3b 8d 29 12 83 f8 07 0f 87 f0 00 00 00 48 0f a3 05 06 89 f5 0e 0f 82 c2 02 00 00 8b 35 ce bc f5 0e 85 f6 0f 85 dd 00 00 00 <48> 8b 44 24 30 65 48 2b 05 dd 8c 29 12 0f 85 02 03 00 00 48 83 c4
RSP: 0018:ffffc900040d70d8 EFLAGS: 00000206
RAX: 0000000000000046 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8de5cea9 RDI: ffffffff8c1b1da0
RBP: ffffffff8e7e7760 R08: 0000000086db7919 R09: 0000000000000007
R10: 0000000000000200 R11: 0000000000000000 R12: 0000000000000002
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
rcu_read_lock include/linux/rcupdate.h:850 [inline]
__update_page_owner_free_handle.isra.0+0x4d/0x4d0 mm/page_owner.c:283
__reset_page_owner+0x93/0x190 mm/page_owner.c:321
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
free_unref_folios+0xaea/0x1790 mm/page_alloc.c:3040
folios_put_refs+0x53c/0x840 mm/swap.c:1002
folio_batch_release include/linux/pagevec.h:101 [inline]
shmem_undo_range+0x5e5/0x1570 mm/shmem.c:1149
shmem_truncate_range mm/shmem.c:1277 [inline]
shmem_evict_inode+0x39e/0xbd0 mm/shmem.c:1407
evict+0x3c2/0xad0 fs/inode.c:846
iput_final fs/inode.c:1966 [inline]
iput.part.0+0x605/0xf50 fs/inode.c:2015
iput+0x35/0x40 fs/inode.c:1981
dentry_unlink_inode+0x2a1/0x490 fs/dcache.c:467
__dentry_kill+0x1d0/0x600 fs/dcache.c:670
finish_dput+0x76/0x480 fs/dcache.c:879
dput.part.0+0x456/0x570 fs/dcache.c:928
dput+0x1f/0x30 fs/dcache.c:920
__fput+0x519/0xb40 fs/file_table.c:477
task_work_run+0x150/0x240 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x8b8/0x2b60 kernel/exit.c:976
do_group_exit+0xd5/0x2a0 kernel/exit.c:1118
get_signal+0x1ec7/0x21e0 kernel/signal.c:3034
arch_do_signal_or_restart+0x91/0x770 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop+0x86/0x4a0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x668/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f405f19c819
RSP: 002b:00007ffe63f10a68 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f405f417da0 RCX: 00007f405f19c819
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f405f417da0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007f405f417cb0 R11: 0000000000000246 R12: 000000000014b49e
R13: 00007f405f41609c R14: 000000000014b46c R15: 00007f405f416090
</TASK>
task:syz-executor state:R running task stack:24128 pid:23414 tgid:23414 ppid:1 task_flags:0x40054c flags:0x00080003
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5298 [inline]
__schedule+0xfee/0x6120 kernel/sched/core.c:6911
preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7238
irqentry_exit+0x17b/0x670 kernel/entry/common.c:239
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:unwind_next_frame+0x17a/0x1ea0 arch/x86/kernel/unwind_orc.c:510
Code: ea 03 0f b6 04 02 4c 89 f2 83 e2 07 38 d0 7f 08 84 c0 0f 85 f7 0a 00 00 48 89 e9 41 0f b6 45 35 48 ba 00 00 00 00 00 fc ff df <48> c1 e9 03 80 3c 11 00 0f 85 8b 16 00 00 4d 8b 7d 48 3c 01 49 83
RSP: 0018:ffffc90011ee7668 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffc90011ee7720
RDX: dffffc0000000000 RSI: ffffffff8c1b1d20 RDI: ffffffff8e1318e8
RBP: ffffc90011ee7720 R08: 0000000086db7919 R09: 0000000000000007
R10: 0000000000000200 R11: 0000000000000000 R12: ffffc90011ee7728
R13: ffffc90011ee76d8 R14: ffffc90011ee770d R15: ffff8880285d1e80
arch_stack_walk+0x94/0xf0 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
save_stack+0x162/0x1e0 mm/page_owner.c:165
__reset_page_owner+0x84/0x190 mm/page_owner.c:320
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
__free_frozen_pages+0x7e1/0x10d0 mm/page_alloc.c:2978
vfree.part.0+0x12b/0x9d0 mm/vmalloc.c:3479
vfree+0x55/0x80 mm/vmalloc.c:3456
kcov_put kernel/kcov.c:442 [inline]
kcov_put kernel/kcov.c:438 [inline]
kcov_close+0x34/0x60 kernel/kcov.c:543
__fput+0x3ff/0xb40 fs/file_table.c:469
task_work_run+0x150/0x240 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x8b8/0x2b60 kernel/exit.c:976
do_group_exit+0xd5/0x2a0 kernel/exit.c:1118
get_signal+0x1ec7/0x21e0 kernel/signal.c:3034
arch_do_signal_or_restart+0x91/0x770 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop+0x86/0x4a0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x668/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f181535d04e
RSP: 002b:00007ffcfcebc618 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: 000000000000037a RBX: 0000555591a58500 RCX: 00007f181535d04e
RDX: 0000000040000000 RSI: 00007ffcfcebc6bc RDI: ffffffffffffffff
RBP: 00007ffcfcebc6bc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000108
R13: 0000555591a6b9f0 R14: 000000000014b4dd R15: 00007ffcfcebc710
</TASK>
rcu: rcu_preempt kthread starved for 6467 jiffies! g200461 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt state:R running task stack:27832 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5298 [inline]
__schedule+0xfee/0x6120 kernel/sched/core.c:6911
__schedule_loop kernel/sched/core.c:6993 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:7008
schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2095
rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2297
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:__orc_find+0xab/0xf0 arch/x86/kernel/unwind_orc.c:111
Code: 75 4b 48 63 13 48 01 da 49 39 d5 73 af 4c 8d 63 fc 49 39 ec 73 b2 4d 29 f7 49 c1 ff 02 4b 8d 14 7f 48 8d 04 50 48 83 c4 08 5b <5d> 41 5c 41 5d 41 5e 41 5f e9 c7 f3 d9 09 48 83 c4 08 31 c0 5b 5d
RSP: 0018:ffffc90000a07cc8 EFLAGS: 00000296
RAX: ffffffff92173478 RBX: 0000000000000002 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff915bde84
RBP: ffffffff915bde88 R08: ffffffff9217347e R09: 0000000000000007
R10: 0000000000000200 R11: 0000000000095cb0 R12: ffffffff915bde84
R13: ffffffff8a5cb0cc R14: ffffffff915bde84 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff888124440000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27e3852753 CR3: 000000002b72e000 CR4: 00000000003526f0
Call Trace:
<IRQ>
orc_find arch/x86/kernel/unwind_orc.c:238 [inline]
unwind_next_frame+0x2ec/0x1ea0 arch/x86/kernel/unwind_orc.c:510
arch_stack_walk+0x94/0xf0 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
unpoison_slab_object mm/kasan/common.c:340 [inline]
__kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4538 [inline]
slab_alloc_node mm/slub.c:4866 [inline]
kmem_cache_alloc_noprof+0x241/0x6e0 mm/slub.c:4873
skb_ext_maybe_cow net/core/skbuff.c:7092 [inline]
skb_ext_add+0xfa/0x810 net/core/skbuff.c:7167
nf_bridge_unshare net/bridge/br_netfilter_hooks.c:169 [inline]
br_nf_forward_ip.part.0+0x28/0x820 net/bridge/br_netfilter_hooks.c:681
br_nf_forward_ip net/bridge/br_netfilter_hooks.c:676 [inline]
br_nf_forward+0xfe5/0x19f0 net/bridge/br_netfilter_hooks.c:773
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_slow+0xbf/0x220 net/netfilter/core.c:623
nf_hook include/linux/netfilter.h:273 [inline]
NF_HOOK include/linux/netfilter.h:316 [inline]
__br_forward+0x2f6/0x970 net/bridge/br_forward.c:115
deliver_clone net/bridge/br_forward.c:131 [inline]
br_flood+0x37f/0x650 net/bridge/br_forward.c:250
br_handle_frame_finish+0xff4/0x1f60 net/bridge/br_input.c:229
br_nf_hook_thresh+0x30d/0x420 net/bridge/br_netfilter_hooks.c:1167
br_nf_pre_routing_finish_ipv6+0x769/0xfb0 net/bridge/br_netfilter_ipv6.c:154
NF_HOOK include/linux/netfilter.h:318 [inline]
br_nf_pre_routing_ipv6+0x39c/0x8b0 net/bridge/br_netfilter_ipv6.c:184
br_nf_pre_routing+0x90d/0x1550 net/bridge/br_netfilter_hooks.c:508
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
br_handle_frame+0xcdd/0x1520 net/bridge/br_input.c:442
__netif_receive_skb_core.constprop.0+0x6c5/0x3550 net/core/dev.c:6068
__netif_receive_skb_one_core+0xb0/0x1e0 net/core/dev.c:6179
__netif_receive_skb+0x1f/0x120 net/core/dev.c:6294
process_backlog+0x37a/0x1580 net/core/dev.c:6645
__napi_poll.constprop.0+0xaf/0x450 net/core/dev.c:7709
napi_poll net/core/dev.c:7772 [inline]
net_rx_action+0xa40/0xf20 net/core/dev.c:7929
handle_softirqs+0x1eb/0x9e0 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0xef/0x150 kernel/softirq.c:723
irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1056
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:63
Code: a8 84 02 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 43 00 1d 00 fb f4 <e9> fc 35 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffc90000197df0 EFLAGS: 00000246
RAX: 00000000018c87c5 RBX: ffff88801e6b0000 RCX: ffffffff8b8e8c75
RDX: 0000000000000000 RSI: ffffffff8de82fd4 RDI: ffffffff8c1b1da0
RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed10170a679d
R10: ffff8880b8533ceb R11: 0000000000000000 R12: 0000000000000001
R13: ffffed1003cd6000 R14: 0000000000000001 R15: ffffffff90d9fc10
arch_safe_halt arch/x86/include/asm/paravirt.h:73 [inline]
default_idle+0x9/0x10 arch/x86/kernel/process.c:767
default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x464/0x590 kernel/sched/idle.c:352
cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:451
start_secondary+0x21d/0x2d0 arch/x86/kernel/smpboot.c:312
common_startup_64+0x13e/0x148
</TASK>
net_ratelimit: 11899 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f6:07:a3:ff:61:53, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:f3:a6:36:2e:63, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f6:07:a3:ff:61:53, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:f3:a6:36:2e:63, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f6:07:a3:ff:61:53, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
net_ratelimit: 14052 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f6:07:a3:ff:61:53, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:f3:a6:36:2e:63, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f6:07:a3:ff:61:53, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:f3:a6:36:2e:63, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:f6:07:a3:ff:61:53, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
---
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [syzbot] [mm?] INFO: rcu detected stall in kcov_ioctl (3)
2026-04-08 23:31 [syzbot] [mm?] INFO: rcu detected stall in kcov_ioctl (3) syzbot
@ 2026-04-08 23:52 ` Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2026-04-08 23:52 UTC (permalink / raw)
To: syzbot
Cc: hannes, jackmanb, linux-kernel, linux-mm, mhocko, surenb,
syzkaller-bugs, vbabka, ziy, Dmitry Vyukov, Andrey Konovalov,
kasan-dev
On Wed, 08 Apr 2026 16:31:27 -0700 syzbot <syzbot+8a59070fc852219166ab@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 7ca6d1cfec80 Merge tag 'powerpc-7.0-4' of git://git.kernel..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=133b4dda580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=64e78d99d9bf8b4c
> dashboard link: https://syzkaller.appspot.com/bug?extid=8a59070fc852219166ab
> compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
>
> Unfortunately, I don't have any reproducer for this issue yet.
Thanks. I added a few kcov names from MAINTAINERS.
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/ace9641c44ac/disk-7ca6d1cf.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6e66f8b9476e/vmlinux-7ca6d1cf.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/d679c066df56/bzImage-7ca6d1cf.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8a59070fc852219166ab@syzkaller.appspotmail.com
>
> bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
> rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
> rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P23414/1:b..l P27649/1:b..l P27664/1:b..l
> rcu: (detected by 0, t=10502 jiffies, g=200461, q=440 ncpus=2)
> task:syz-executor state:R running task stack:25416 pid:27664 tgid:27664 ppid:5809 task_flags:0x400000 flags:0x00080000
> Call Trace:
> <TASK>
> context_switch kernel/sched/core.c:5298 [inline]
> __schedule+0xfee/0x6120 kernel/sched/core.c:6911
> preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7238
> irqentry_exit+0x17b/0x670 kernel/entry/common.c:239
> asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
> RIP: 0010:__orc_find+0x49/0xf0 arch/x86/kernel/unwind_orc.c:101
> Code: 00 49 89 fe 48 89 f0 49 39 fc 72 7b 48 b9 00 00 00 00 00 fc ff df 49 89 ff 48 89 fd eb 0c 48 8d 6b 04 49 89 df 49 39 ec 72 4e <4c> 89 e2 48 29 ea 48 89 d6 48 c1 ea 3f 48 c1 fe 02 48 01 f2 48 d1
> RSP: 0018:ffffc9000d12f138 EFLAGS: 00000212
> RAX: ffffffff91777f46 RBX: ffffffff90f165c4 RCX: dffffc0000000000
> RDX: ffffffff81aecd9f RSI: 0000000000000000 RDI: ffffffff90f165b8
> RBP: ffffffff90f165b8 R08: ffffffff91777f70 R09: 0000000000000007
> R10: 0000000000000200 R11: 000000000000aecd R12: ffffffff90f165c0
> R13: ffffffff81aecd22 R14: ffffffff90f165b8 R15: ffffffff90f165b8
> orc_find arch/x86/kernel/unwind_orc.c:238 [inline]
> unwind_next_frame+0x2ec/0x1ea0 arch/x86/kernel/unwind_orc.c:510
> __unwind_start+0x3d1/0x7f0 arch/x86/kernel/unwind_orc.c:773
> unwind_start arch/x86/include/asm/unwind.h:64 [inline]
> arch_stack_walk+0x73/0xf0 arch/x86/kernel/stacktrace.c:24
> stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
> save_stack+0x162/0x1e0 mm/page_owner.c:165
> __set_page_owner+0x8c/0x540 mm/page_owner.c:341
> set_page_owner include/linux/page_owner.h:32 [inline]
> post_alloc_hook+0x153/0x170 mm/page_alloc.c:1889
> prep_new_page mm/page_alloc.c:1897 [inline]
> get_page_from_freelist+0x111d/0x3140 mm/page_alloc.c:3962
> __alloc_frozen_pages_noprof+0x27c/0x2ba0 mm/page_alloc.c:5250
> __alloc_pages_noprof mm/page_alloc.c:5284 [inline]
> alloc_pages_bulk_noprof+0x782/0x1490 mm/page_alloc.c:5204
> ___alloc_pages_bulk mm/kasan/shadow.c:345 [inline]
> __kasan_populate_vmalloc_do mm/kasan/shadow.c:370 [inline]
> __kasan_populate_vmalloc+0xf0/0x210 mm/kasan/shadow.c:424
> kasan_populate_vmalloc include/linux/kasan.h:580 [inline]
> alloc_vmap_area+0x95d/0x2bd0 mm/vmalloc.c:2129
> __get_vm_area_node+0x1ca/0x330 mm/vmalloc.c:3232
> __vmalloc_node_range_noprof+0x213/0x1530 mm/vmalloc.c:4024
> vmalloc_user_noprof+0x9e/0xe0 mm/vmalloc.c:4218
> kcov_ioctl+0x4c/0x720 kernel/kcov.c:726
> vfs_ioctl fs/ioctl.c:51 [inline]
I assume the fuzzer is asking kcov_ioctl() to allocate ludicrous
amounts of memory.
case KCOV_INIT_TRACE:
/*
* Enable kcov in trace mode and setup buffer size.
* Must happen before anything else.
*
* First check the size argument - it must be at least 2
* to hold the current position and one PC.
*/
size = arg;
if (size < 2 || size > INT_MAX / sizeof(unsigned long))
return -EINVAL;
area = vmalloc_user(size * sizeof(unsigned long));
KCOV_REMOTE_MAX_HANDLES looks to be OK.
/sys/debug/kcov is mode 0600 so this is no emergency.
Maintainers, perhaps we can do something more ... restrained here?
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-04-08 23:52 UTC | newest]
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2026-04-08 23:31 [syzbot] [mm?] INFO: rcu detected stall in kcov_ioctl (3) syzbot
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