* [syzbot] [kernel?] BUG: soft lockup in gate_timer_func
@ 2026-08-17 16:04 syzbot
2026-08-18 4:45 ` Edward Adam Davis
` (3 more replies)
0 siblings, 4 replies; 8+ messages in thread
From: syzbot @ 2026-08-17 16:04 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: 21d6ac051080 Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=10a50679580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d1128bc53f2ef7f3
dashboard link: https://syzkaller.appspot.com/bug?extid=0054fed3dc9085390f51
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15911a25580000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0054fed3dc9085390f51@syzkaller.appspotmail.com
watchdog: BUG: soft lockup - CPU#1 stuck for 3s! [syz-executor291:5020]
Modules linked in:
irq event stamp: 4562887
hardirqs last enabled at (4562886): [<ffff800080557c84>] seqcount_lockdep_reader_access+0x7c/0xf8 include/linux/seqlock.h:75
hardirqs last disabled at (4562887): [<ffff80008690b4b4>] __el1_irq arch/arm64/kernel/entry-common.c:527 [inline]
hardirqs last disabled at (4562887): [<ffff80008690b4b4>] el1_interrupt+0x28/0x60 arch/arm64/kernel/entry-common.c:543
softirqs last enabled at (14246): [<ffff800084c0e6c4>] __alloc_skb+0x1c0/0x610 net/core/skbuff.c:698
softirqs last disabled at (14249): [<ffff8000800204c0>] __do_softirq+0x14/0x20 kernel/softirq.c:656
CPU: 1 UID: 0 PID: 5020 Comm: syz-executor291 Not tainted syzkaller #0 PREEMPT
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 43400005 (nZcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : seqcount_lockdep_reader_access+0xd8/0xf8 include/linux/seqlock.h:76
lr : seqcount_lockdep_reader_access+0xd4/0xf8 include/linux/seqlock.h:75
sp : ffff80008eb77ce0
x29: ffff80008eb77ce0 x28: 1fffe00034bbc63a x27: ffff80008e853110
x26: dfff800000000000 x25: ffff0000c1b62b80 x24: 1fffe0001ad59fa6
x23: dfff800000000000 x22: ffff0000c1b62bb0 x21: 0000000000000000
x20: ffff8000805580e8 x19: 00000000000000c0 x18: 0000000000000000
x17: ffff80008a7d6000 x16: 0000000000000002 x15: ffff80008a35fda0
x14: ffff80008a5d5e28 x13: 0000000000000001 x12: ffff0000d5af8000
x11: ffff80008a5d5e28 x10: 0000000000000003 x9 : 0000000000000101
x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000001 x4 : 0000000000000008 x3 : ffff800080557cd4
x2 : 0000000000000080 x1 : ffff0000d5af8000 x0 : 0000000000000000
Call trace:
__daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline] (P)
arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] (P)
seqcount_lockdep_reader_access+0xd8/0xf8 include/linux/seqlock.h:75 (P)
ktime_get+0x68/0x218 kernel/time/timekeeping.c:971
gate_get_time+0x1c/0xa4 net/sched/act_gate.c:23
gate_timer_func+0x1a8/0x390 net/sched/act_gate.c:101
__run_hrtimer kernel/time/hrtimer.c:2032 [inline]
__hrtimer_run_queues+0x314/0xbe0 kernel/time/hrtimer.c:2096
hrtimer_run_softirq+0x15c/0x21c kernel/time/hrtimer.c:2113
handle_softirqs+0x2ec/0xd98 kernel/softirq.c:622
__do_softirq+0x14/0x20 kernel/softirq.c:656
____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:78
call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:885
do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:83
invoke_softirq kernel/softirq.c:503 [inline]
__irq_exit_rcu+0x1ac/0x428 kernel/softirq.c:735
irq_exit_rcu+0x14/0x84 kernel/softirq.c:752
__el1_irq arch/arm64/kernel/entry-common.c:531 [inline]
el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:543
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:548
el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:586
__daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline] (P)
arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline] (P)
__local_bh_enable_ip+0x1f0/0x35c kernel/softirq.c:455 (P)
local_bh_enable include/linux/bottom_half.h:33 [inline]
__alloc_skb+0x1c8/0x610 net/core/skbuff.c:699
alloc_skb include/linux/skbuff.h:1384 [inline]
alloc_skb_with_frags+0xb8/0x690 net/core/skbuff.c:6775
sock_alloc_send_pskb+0x740/0x850 net/core/sock.c:3012
unix_dgram_sendmsg+0x434/0x1078 net/unix/af_unix.c:2137
sock_sendmsg_nosec net/socket.c:775 [inline]
__sock_sendmsg+0xc8/0x17c net/socket.c:790
__sys_sendto+0x250/0x328 net/socket.c:2252
__do_sys_sendto net/socket.c:2259 [inline]
__se_sys_sendto net/socket.c:2255 [inline]
__arm64_sys_sendto+0xec/0x10c net/socket.c:2255
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle_call+0xd0/0xfc kernel/sched/idle.c:129
watchdog: BUG: soft lockup - CPU#1 stuck for 6s! [syz-executor291:5020]
Modules linked in:
irq event stamp: 9755971
hardirqs last enabled at (9755970): [<ffff800086930818>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
hardirqs last enabled at (9755970): [<ffff800086930818>] _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:198
hardirqs last disabled at (9755971): [<ffff80008690b4b4>] __el1_irq arch/arm64/kernel/entry-common.c:527 [inline]
hardirqs last disabled at (9755971): [<ffff80008690b4b4>] el1_interrupt+0x28/0x60 arch/arm64/kernel/entry-common.c:543
softirqs last enabled at (14246): [<ffff800084c0e6c4>] __alloc_skb+0x1c0/0x610 net/core/skbuff.c:698
softirqs last disabled at (14249): [<ffff8000800204c0>] __do_softirq+0x14/0x20 kernel/softirq.c:656
CPU: 1 UID: 0 PID: 5020 Comm: syz-executor291 Tainted: G L syzkaller #0 PREEMPT
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
pc : _raw_spin_unlock_irqrestore+0x44/0x98 kernel/locking/spinlock.c:198
lr : __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
lr : _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:198
sp : ffff80008eb77dc0
x29: ffff80008eb77dc0 x28: 1fffe00034bbc63a x27: ffff0001a5de31c0
x26: ffff0001a5de31d0 x25: ffff0000d6acfd38 x24: dfff800000000000
x23: 0000000000000001 x22: ffff800084ec6bfc x21: ffff0001a5de2d80
x20: ffff0001a5de2d80 x19: 0000000000000000 x18: 0000000000000000
x17: ffff80008a7d6000 x16: 0000000000000004 x15: ffff80008a35fda0
x14: 000000008030dda8 x13: 0000000000000001 x12: 0000000000000000
x11: ffff800080156070 x10: 0000000000000003 x9 : 0000000000000000
x8 : 00000000000000c0 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000001 x4 : 0000000000000008 x3 : ffff800080156118
x2 : 0000000000000000 x1 : ffff0000d5af8000 x0 : ffff80011d2fd000
Call trace:
__daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline] (P)
arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] (P)
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline] (P)
_raw_spin_unlock_irqrestore+0x44/0x98 kernel/locking/spinlock.c:198 (P)
__run_hrtimer kernel/time/hrtimer.c:2028 [inline]
__hrtimer_run_queues+0x22c/0xbe0 kernel/time/hrtimer.c:2096
hrtimer_run_softirq+0x15c/0x21c kernel/time/hrtimer.c:2113
handle_softirqs+0x2ec/0xd98 kernel/softirq.c:622
__do_softirq+0x14/0x20 kernel/softirq.c:656
____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:78
call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:885
do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:83
invoke_softirq kernel/softirq.c:503 [inline]
__irq_exit_rcu+0x1ac/0x428 kernel/softirq.c:735
irq_exit_rcu+0x14/0x84 kernel/softirq.c:752
__el1_irq arch/arm64/kernel/entry-common.c:531 [inline]
el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:543
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:548
el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:586
__daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline] (P)
arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline] (P)
__local_bh_enable_ip+0x1f0/0x35c kernel/softirq.c:455 (P)
local_bh_enable include/linux/bottom_half.h:33 [inline]
__alloc_skb+0x1c8/0x610 net/core/skbuff.c:699
alloc_skb include/linux/skbuff.h:1384 [inline]
alloc_skb_with_frags+0xb8/0x690 net/core/skbuff.c:6775
sock_alloc_send_pskb+0x740/0x850 net/core/sock.c:3012
unix_dgram_sendmsg+0x434/0x1078 net/unix/af_unix.c:2137
sock_sendmsg_nosec net/socket.c:775 [inline]
__sock_sendmsg+0xc8/0x17c net/socket.c:790
__sys_sendto+0x250/0x328 net/socket.c:2252
__do_sys_sendto net/socket.c:2259 [inline]
__se_sys_sendto net/socket.c:2255 [inline]
__arm64_sys_sendto+0xec/0x10c net/socket.c:2255
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle_call+0xd0/0xfc kernel/sched/idle.c:129
watchdog: BUG: soft lockup - CPU#1 stuck for 9s! [syz-executor291:5020]
Modules linked in:
irq event stamp: 14939657
hardirqs last enabled at (14939656): [<ffff800086930818>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
hardirqs last enabled at (14939656): [<ffff800086930818>] _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:198
hardirqs last disabled at (14939657): [<ffff80008690b4b4>] __el1_irq arch/arm64/kernel/entry-common.c:527 [inline]
hardirqs last disabled at (14939657): [<ffff80008690b4b4>] el1_interrupt+0x28/0x60 arch/arm64/kernel/entry-common.c:543
softirqs last enabled at (14246): [<ffff800084c0e6c4>] __alloc_skb+0x1c0/0x610 net/core/skbuff.c:698
softirqs last disabled at (14249): [<ffff8000800204c0>] __do_softirq+0x14/0x20 kernel/softirq.c:656
CPU: 1 UID: 0 PID: 5020 Comm: syz-executor291 Tainted: G L syzkaller #0 PREEMPT
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
pc : _raw_spin_unlock_irqrestore+0x44/0x98 kernel/locking/spinlock.c:198
lr : __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
lr : _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:198
sp : ffff80008eb77dc0
x29: ffff80008eb77dc0 x28: 1fffe00034bbc63a x27: ffff0001a5de31c0
x26: ffff0001a5de31d0 x25: ffff0000d6acfd38 x24: dfff800000000000
x23: 0000000000000001 x22: ffff800084ec6bfc x21: ffff0001a5de2d80
x20: ffff0001a5de2d80 x19: 0000000000000000 x18: 0000000000000000
x17: ffff80008a7d6000 x16: 0000000000000004 x15: ffff80008a35fda0
x14: 000000008030dda8 x13: 0000000000000001 x12: 0000000000000000
x11: ffff800080156070 x10: 0000000000000003 x9 : 0000000000000000
x8 : 00000000000000c0 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000001 x4 : 0000000000000008 x3 : ffff800080156118
x2 : 0000000000000000 x1 : ffff0000d5af8000 x0 : ffff80011d2fd000
Call trace:
__daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline] (P)
arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] (P)
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline] (P)
_raw_spin_unlock_irqrestore+0x44/0x98 kernel/locking/spinlock.c:198 (P)
__run_hrtimer kernel/time/hrtimer.c:2028 [inline]
__hrtimer_run_queues+0x22c/0xbe0 kernel/time/hrtimer.c:2096
hrtimer_run_softirq+0x15c/0x21c kernel/time/hrtimer.c:2113
handle_softirqs+0x2ec/0xd98 kernel/softirq.c:622
__do_softirq+0x14/0x20 kernel/softirq.c:656
____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:78
call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:885
do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:83
invoke_softirq kernel/softirq.c:503 [inline]
__irq_exit_rcu+0x1ac/0x428 kernel/softirq.c:735
irq_exit_rcu+0x14/0x84 kernel/softirq.c:752
__el1_irq arch/arm64/kernel/entry-common.c:531 [inline]
el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:543
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:548
el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:586
__daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline] (P)
arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline] (P)
__local_bh_enable_ip+0x1f0/0x35c kernel/softirq.c:455 (P)
local_bh_enable include/linux/bottom_half.h:33 [inline]
__alloc_skb+0x1c8/0x610 net/core/skbuff.c:699
alloc_skb include/linux/skbuff.h:1384 [inline]
alloc_skb_with_frags+0xb8/0x690 net/core/skbuff.c:6775
sock_alloc_send_pskb+0x740/0x850 net/core/sock.c:3012
unix_dgram_sendmsg+0x434/0x1078 net/unix/af_unix.c:2137
sock_sendmsg_nosec net/socket.c:775 [inline]
__sock_sendmsg+0xc8/0x17c net/socket.c:790
__sys_sendto+0x250/0x328 net/socket.c:2252
__do_sys_sendto net/socket.c:2259 [inline]
__se_sys_sendto net/socket.c:2255 [inline]
__arm64_sys_sendto+0xec/0x10c net/socket.c:2255
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle_call+0xd0/0xfc kernel/sched/idle.c:129
watchdog: BUG: soft lockup - CPU#1 stuck for 12s! [syz-executor291:5020]
Modules linked in:
irq event stamp: 20130019
hardirqs last enabled at (20130018): [<ffff800086930818>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
hardirqs last enabled at (20130018): [<ffff800086930818>] _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:198
hardirqs last disabled at (20130019): [<ffff80008690b4b4>] __el1_irq arch/arm64/kernel/entry-common.c:527 [inline]
hardirqs last disabled at (20130019): [<ffff80008690b4b4>] el1_interrupt+0x28/0x60 arch/arm64/kernel/entry-common.c:543
softirqs last enabled at (14246): [<ffff800084c0e6c4>] __alloc_skb+0x1c0/0x610 net/core/skbuff.c:698
softirqs last disabled at (14249): [<ffff8000800204c0>] __do_softirq+0x14/0x20 kernel/softirq.c:656
CPU: 1 UID: 0 PID: 5020 Comm: syz-executor291 Tainted: G L syzkaller #0 PREEMPT
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
pc : _raw_spin_unlock_irqrestore+0x44/0x98 kernel/locking/spinlock.c:198
lr : __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
lr : _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:198
sp : ffff80008eb77dc0
x29: ffff80008eb77dc0 x28: 1fffe00034bbc63a x27: ffff0001a5de31c0
x26: ffff0001a5de31d0 x25: ffff0000d6acfd38 x24: dfff800000000000
x23: 0000000000000001 x22: ffff800084ec6bfc x21: ffff0001a5de2d80
x20: ffff0001a5de2d80 x19: 0000000000000000 x18: 0000000000000000
x17: ffff80008a7d6000 x16: 0000000000000004 x15: ffff80008a35fda0
x14: 000000008030dda8 x13: 0000000000000001 x12: 0000000000000000
x11: ffff800080156070 x10: 0000000000000003 x9 : 0000000000000000
x8 : 00000000000000c0 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000001 x4 : 0000000000000008 x3 : ffff800080156118
x2 : 0000000000000000 x1 : ffff0000d5af8000 x0 : ffff80011d2fd000
Call trace:
__daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline] (P)
arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] (P)
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline] (P)
_raw_spin_unlock_irqrestore+0x44/0x98 kernel/locking/spinlock.c:198 (P)
__run_hrtimer kernel/time/hrtimer.c:2028 [inline]
__hrtimer_run_queues+0x22c/0xbe0 kernel/time/hrtimer.c:2096
hrtimer_run_softirq+0x15c/0x21c kernel/time/hrtimer.c:2113
handle_softirqs+0x2ec/0xd98 kernel/softirq.c:622
__do_softirq+0x14/0x20 kernel/softirq.c:656
____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:78
call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:885
do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:83
invoke_softirq kernel/softirq.c:503 [inline]
__irq_exit_rcu+0x1ac/0x428 kernel/softirq.c:735
irq_exit_rcu+0x14/0x84 kernel/softirq.c:752
__el1_irq arch/arm64/kernel/entry-common.c:531 [inline]
el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:543
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:548
el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:586
__daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline] (P)
arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline] (P)
__local_bh_enable_ip+0x1f0/0x35c kernel/softirq.c:455 (P)
local_bh_enable include/linux/bottom_half.h:33 [inline]
__alloc_skb+0x1c8/0x610 net/core/skbuff.c:699
alloc_skb include/linux/skbuff.h:1384 [inline]
alloc_skb_with_frags+0xb8/0x690 net/core/skbuff.c:6775
sock_alloc_send_pskb+0x740/0x850 net/core/sock.c:3012
unix_dgram_sendmsg+0x434/0x1078 net/unix/af_unix.c:2137
sock_sendmsg_nosec net/socket.c:775 [inline]
__sock_sendmsg+0xc8/0x17c net/socket.c:790
__sys_sendto+0x250/0x328 net/socket.c:2252
__do_sys_sendto net/socket.c:2259 [inline]
__se_sys_sendto net/socket.c:2255 [inline]
__arm64_sys_sendto+0xec/0x10c net/socket.c:2255
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle_call+0xd0/0xfc kernel/sched/idle.c:129
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [syzbot] [kernel?] BUG: soft lockup in gate_timer_func
2026-08-17 16:04 [syzbot] [kernel?] BUG: soft lockup in gate_timer_func syzbot
@ 2026-08-18 4:45 ` Edward Adam Davis
2026-08-18 6:34 ` syzbot
2026-08-18 8:24 ` Edward Adam Davis
` (2 subsequent siblings)
3 siblings, 1 reply; 8+ messages in thread
From: Edward Adam Davis @ 2026-08-18 4:45 UTC (permalink / raw)
To: syzbot+0054fed3dc9085390f51; +Cc: linux-kernel, syzkaller-bugs
#syz test
diff --git a/net/sched/act_gate.c b/net/sched/act_gate.c
index fdbfcaa3e2ab..9065e7b88156 100644
--- a/net/sched/act_gate.c
+++ b/net/sched/act_gate.c
@@ -88,7 +88,8 @@ static enum hrtimer_restart gate_timer_func(struct hrtimer *timer)
gact->current_max_octets = next->maxoctets;
gact->current_close_time = ktime_add_ns(gact->current_close_time,
- next->interval);
+ next->interval < 100 ?
+ 100 : next->interval);
close_time = gact->current_close_time;
@@ -101,10 +102,10 @@ static enum hrtimer_restart gate_timer_func(struct hrtimer *timer)
now = gate_get_time(gact);
if (ktime_after(now, close_time)) {
- ktime_t cycle, base;
+ u64 cycle, base;
u64 n;
- cycle = p->tcfg_cycletime;
+ cycle = p->tcfg_cycletime > 20 ? 20 : p->tcfg_cycletime;
base = ns_to_ktime(p->tcfg_basetime);
n = div64_u64(ktime_sub_ns(now, base), cycle);
close_time = ktime_add_ns(base, (n + 1) * cycle);
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [syzbot] [kernel?] BUG: soft lockup in gate_timer_func
2026-08-17 16:04 [syzbot] [kernel?] BUG: soft lockup in gate_timer_func syzbot
2026-08-18 4:45 ` Edward Adam Davis
@ 2026-08-18 8:24 ` Edward Adam Davis
2026-08-18 8:50 ` syzbot
2026-08-18 9:37 ` Edward Adam Davis
2026-08-18 10:44 ` [PATCH] net/sched: act_gate: Limit the max value for cycletime Edward Adam Davis
3 siblings, 1 reply; 8+ messages in thread
From: Edward Adam Davis @ 2026-08-18 8:24 UTC (permalink / raw)
To: syzbot+0054fed3dc9085390f51; +Cc: linux-kernel, syzkaller-bugs
#syz test
diff --git a/net/sched/act_gate.c b/net/sched/act_gate.c
index fdbfcaa3e2ab..6b8adfbf9c2d 100644
--- a/net/sched/act_gate.c
+++ b/net/sched/act_gate.c
@@ -178,6 +178,10 @@ static const struct nla_policy gate_policy[TCA_GATE_MAX + 1] = {
[TCA_GATE_CLOCKID] = { .type = NLA_S32 },
};
+#ifndef __NET_TC_GATE_LIMIT
+#define GATE_ENTRY_INTERVAL_MIN 100
+#endif
+
static int fill_gate_entry(struct nlattr **tb, struct tcfg_gate_entry *entry,
struct netlink_ext_ack *extack)
{
@@ -188,7 +192,7 @@ static int fill_gate_entry(struct nlattr **tb, struct tcfg_gate_entry *entry,
if (tb[TCA_GATE_ENTRY_INTERVAL])
interval = nla_get_u32(tb[TCA_GATE_ENTRY_INTERVAL]);
- if (interval == 0) {
+ if (interval < GATE_ENTRY_INTERVAL_MIN) {
NL_SET_ERR_MSG(extack, "Invalid interval for schedule entry");
return -EINVAL;
}
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [syzbot] [kernel?] BUG: soft lockup in gate_timer_func
2026-08-17 16:04 [syzbot] [kernel?] BUG: soft lockup in gate_timer_func syzbot
2026-08-18 4:45 ` Edward Adam Davis
2026-08-18 8:24 ` Edward Adam Davis
@ 2026-08-18 9:37 ` Edward Adam Davis
2026-08-18 10:44 ` syzbot
2026-08-18 10:44 ` [PATCH] net/sched: act_gate: Limit the max value for cycletime Edward Adam Davis
3 siblings, 1 reply; 8+ messages in thread
From: Edward Adam Davis @ 2026-08-18 9:37 UTC (permalink / raw)
To: syzbot+0054fed3dc9085390f51; +Cc: linux-kernel, syzkaller-bugs
#syz test
diff --git a/net/sched/act_gate.c b/net/sched/act_gate.c
index fdbfcaa3e2ab..ad5a6d75bbda 100644
--- a/net/sched/act_gate.c
+++ b/net/sched/act_gate.c
@@ -501,6 +501,8 @@ static int tcf_gate_init(struct net *net, struct nlattr *nla,
cycle = ktime_add_ns(cycle, entry->interval);
cycletime = cycle;
}
+ if (cycletime > S64_MAX)
+ cycletime = S64_MAX;
p->tcfg_cycletime = cycletime;
p->tcfg_cycletime_ext = cycletime_ext;
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH] net/sched: act_gate: Limit the max value for cycletime
2026-08-17 16:04 [syzbot] [kernel?] BUG: soft lockup in gate_timer_func syzbot
` (2 preceding siblings ...)
2026-08-18 9:37 ` Edward Adam Davis
@ 2026-08-18 10:44 ` Edward Adam Davis
3 siblings, 0 replies; 8+ messages in thread
From: Edward Adam Davis @ 2026-08-18 10:44 UTC (permalink / raw)
To: syzbot+0054fed3dc9085390f51
Cc: jhs, jiri, davem, edumazet, kuba, pabeni, horms, Po.Liu, netdev,
linux-kernel, syzkaller-bugs
If the user passes a cycletime value of 0xFFFFFFFFFFFFFFFFULL,
an overflow occurs during the assignment of cycle in gate_timer_func():
cycle = p->tcfg_cycletime; // overflow, cycle = -1
Since the local variable cycle is declared as ktime_t (i.e., s64),
the assignment overflows.
This leads to an incorrect calculation of the close_time value.
Ultimately, the new hrtimer expiry time becomes less than now, causing
__hrtimer_run_queues() to execute the "timer callback" for an excessively
long period, which triggers a soft lockup. [1]
Another factor is that the passed interval value is 1; while this accelerates
the problematic progression of close_time, it is not the decisive factor in
the issue described in [1].
When initializing cycletime, ensuring its value does not exceed S64_MAX
guarantees that the hrtimer can correctly calculate a valid expiry time.
[1]
watchdog: BUG: soft lockup - CPU#1 stuck for 3s! [syz-executor291:5020]
pc : seqcount_lockdep_reader_access+0xd8/0xf8 include/linux/seqlock.h:76
Call trace:
arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] (P)
seqcount_lockdep_reader_access+0xd8/0xf8 include/linux/seqlock.h:75 (P)
ktime_get+0x68/0x218 kernel/time/timekeeping.c:971
gate_get_time+0x1c/0xa4 net/sched/act_gate.c:23
gate_timer_func+0x1a8/0x390 net/sched/act_gate.c:101
__run_hrtimer kernel/time/hrtimer.c:2032 [inline]
__hrtimer_run_queues+0x314/0xbe0 kernel/time/hrtimer.c:2096
hrtimer_run_softirq+0x15c/0x21c kernel/time/hrtimer.c:2113
handle_softirqs+0x2ec/0xd98 kernel/softirq.c:622
__do_softirq+0x14/0x20 kernel/softirq.c:656
____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:78
call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:885
do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:83
invoke_softirq kernel/softirq.c:503 [inline]
__irq_exit_rcu+0x1ac/0x428 kernel/softirq.c:735
irq_exit_rcu+0x14/0x84 kernel/softirq.c:752
__el1_irq arch/arm64/kernel/entry-common.c:531 [inline]
el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:543
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:548
el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:586
__daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline] (P)
arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline] (P)
__local_bh_enable_ip+0x1f0/0x35c kernel/softirq.c:455 (P)
local_bh_enable include/linux/bottom_half.h:33 [inline]
__alloc_skb+0x1c8/0x610 net/core/skbuff.c:699
alloc_skb include/linux/skbuff.h:1384 [inline]
alloc_skb_with_frags+0xb8/0x690 net/core/skbuff.c:6775
sock_alloc_send_pskb+0x740/0x850 net/core/sock.c:3012
unix_dgram_sendmsg+0x434/0x1078 net/unix/af_unix.c:2137
sock_sendmsg_nosec net/socket.c:775 [inline]
Fixes: a51c328df310 ("net: qos: introduce a gate control flow action")
Reported-by: syzbot+0054fed3dc9085390f51@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0054fed3dc9085390f51
Tested-by: syzbot+0054fed3dc9085390f51@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
net/sched/act_gate.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/sched/act_gate.c b/net/sched/act_gate.c
index fdbfcaa3e2ab..ad5a6d75bbda 100644
--- a/net/sched/act_gate.c
+++ b/net/sched/act_gate.c
@@ -501,6 +501,8 @@ static int tcf_gate_init(struct net *net, struct nlattr *nla,
cycle = ktime_add_ns(cycle, entry->interval);
cycletime = cycle;
}
+ if (cycletime > S64_MAX)
+ cycletime = S64_MAX;
p->tcfg_cycletime = cycletime;
p->tcfg_cycletime_ext = cycletime_ext;
--
2.43.0
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2026-08-18 10:44 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2026-08-17 16:04 [syzbot] [kernel?] BUG: soft lockup in gate_timer_func syzbot
2026-08-18 4:45 ` Edward Adam Davis
2026-08-18 6:34 ` syzbot
2026-08-18 8:24 ` Edward Adam Davis
2026-08-18 8:50 ` syzbot
2026-08-18 9:37 ` Edward Adam Davis
2026-08-18 10:44 ` syzbot
2026-08-18 10:44 ` [PATCH] net/sched: act_gate: Limit the max value for cycletime Edward Adam Davis
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