syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (2 ticks this GP) idle=118c/1/0x4000000000000000 softirq=19192/19199 fqs=1
rcu: 	(detected by 0, t=10504 jiffies, g=13697, q=690 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 5232 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:taprio_set_budgets+0x1bc/0x3b0 net/sched/sch_taprio.c:674
Code: 25 f8 41 bd ff ff ff 7f 4d 89 f7 e9 9c 00 00 00 e8 19 30 25 f8 4c 89 e8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 <4d> 89 f7 74 08 4c 89 ef e8 47 99 88 f8 4d 69 6d 00 e8 03 00 00 4c
RSP: 0018:ffffc90000a08c00 EFLAGS: 00000046
RAX: 1ffff110043d5600 RBX: 0000000000000000 RCX: dffffc0000000000
RDX: 0000000000010000 RSI: 00000000000000ff RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200014117c R12: 0000000000000000
R13: ffff888021eab000 R14: ffff888021eab000 R15: 00000000000000ff
FS:  00007fe159d47880(0000) GS:ffff888125d1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000600 CR3: 00000000507e0000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 advance_sched+0x963/0xc90 net/sched/sch_taprio.c:982
 __run_hrtimer kernel/time/hrtimer.c:1761 [inline]
 __hrtimer_run_queues+0x52c/0xc60 kernel/time/hrtimer.c:1825
 hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1887
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1039 [inline]
 __sysvec_apic_timer_interrupt+0x108/0x410 arch/x86/kernel/apic/apic.c:1056
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1050
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:do_inode_permission fs/namei.c:524 [inline]
RIP: 0010:inode_permission+0x66/0x470 fs/namei.c:593
Code: e5 02 0f 85 1d 01 00 00 e8 b7 c3 88 ff 49 8d 6e 02 49 89 ec 49 c1 ec 03 43 0f b6 04 3c 84 c0 0f 85 0d 03 00 00 44 0f b7 7d 00 <44> 89 fe 83 e6 01 31 ff e8 2d c7 88 ff 41 83 e7 01 0f 84 8c 01 00
RSP: 0018:ffffc90003097a80 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000081 RCX: ffff8880506e9e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff888148cf8c2a R08: ffff88801dea9c20 R09: ffff888022e4c2f0
R10: ffff88801dea9c20 R11: ffff888022e4c2f0 R12: 1ffff1102919f185
R13: 0000000000000000 R14: ffff888148cf8c28 R15: 000000000000002b
 may_lookup fs/namei.c:1836 [inline]
 link_path_walk+0x232/0xea0 fs/namei.c:2445
 path_lookupat+0x97/0x430 fs/namei.c:2653
 filename_lookup+0x212/0x570 fs/namei.c:2683
 do_readlinkat+0xd9/0x500 fs/stat.c:576
 __do_sys_readlink fs/stat.c:613 [inline]
 __se_sys_readlink fs/stat.c:610 [inline]
 __x64_sys_readlink+0x7f/0x90 fs/stat.c:610
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe1597153a7
Code: 00 00 90 48 83 ec 10 48 63 ff 45 31 c9 45 31 c0 6a 00 31 c9 e8 8a 20 f9 ff 48 83 c4 18 c3 0f 1f 44 00 00 b8 59 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 8b 15 21 ba 0d 00 f7 d8 64 89 02 48
RSP: 002b:00007ffdb8e62a78 EFLAGS: 00000246 ORIG_RAX: 0000000000000059
RAX: ffffffffffffffda RBX: 00007ffdb8e62f50 RCX: 00007fe1597153a7
RDX: 0000000000000400 RSI: 00007ffdb8e62a80 RDI: 00007ffdb8e62f50
RBP: 00007ffdb8e62a80 R08: 000055dccced4034 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000400
R13: 0000000000000100 R14: 000055dca8f7fbe0 R15: 00007ffdb8e639d0
 </TASK>
rcu: rcu_preempt kthread starved for 10499 jiffies! g13697 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:27160 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7058
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 5977 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:check_kcov_mode kernel/kcov.c:194 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x37/0x70 kernel/kcov.c:217
Code: 08 50 a0 92 65 8b 15 e8 a3 e0 10 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 3c 16 00 00 00 74 2c 8b 91 18 16 00 00 <83> fa 02 75 21 48 8b 91 20 16 00 00 48 8b 32 48 8d 7e 01 8b 89 1c
RSP: 0018:ffffc90003e4f538 EFLAGS: 00000246
RAX: ffffffff81b44deb RBX: 1ffff110170e7f61 RCX: ffff88802bd55a00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90003e4f6c0 R08: ffffffff8fa37e37 R09: 1ffffffff1f46fc6
R10: dffffc0000000000 R11: fffffbfff1f46fc7 R12: ffff8880b873fb08
R13: dffffc0000000000 R14: ffff8880b863b1c0 R15: 0000000000000001
FS:  000055558ad41500(0000) GS:ffff888125c1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fed09ce56c0 CR3: 0000000027fb2000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 csd_lock_wait kernel/smp.c:342 [inline]
 smp_call_function_many_cond+0xd4b/0x12d0 kernel/smp.c:877
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1044
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:91 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline]
 flush_tlb_mm_range+0x6b1/0x12d0 arch/x86/mm/tlb.c:1451
 dup_mmap+0x15a0/0x1ac0 mm/mmap.c:1873
 dup_mm kernel/fork.c:1485 [inline]
 copy_mm+0x13c/0x4b0 kernel/fork.c:1537
 copy_process+0x1706/0x3c00 kernel/fork.c:2175
 kernel_clone+0x21e/0x840 kernel/fork.c:2605
 __do_sys_clone kernel/fork.c:2748 [inline]
 __se_sys_clone kernel/fork.c:2732 [inline]
 __x64_sys_clone+0x18b/0x1e0 kernel/fork.c:2732
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fed08f85453
Code: 1f 84 00 00 00 00 00 64 48 8b 04 25 10 00 00 00 45 31 c0 31 d2 31 f6 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 89 c2 85 c0 75 2c 64 48 8b 04 25 10 00 00
RSP: 002b:00007ffd1ac54da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fed08f85453
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001
R10: 000055558ad417d0 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000000927c0 R14: 000000000001c0d8 R15: 00007ffd1ac54f40
 </TASK>