Dear Developers, I am reporting an RCU CPU stall detected during fuzzing with Syzkaller on Linux 6.18.0-rc.
Technical Summary: The stall occurs on CPU 0 while executing a clone syscall. The task was interrupted by a timer softirq which then invoked mac80211_hwsim_beacon. The trace shows it is stuck waiting for a spinlock in mac80211_hwsim_tx_frame_no_nl. Key Logs: RCU GP Starvation: 10509 jiffies Call Trace: native_queued_spin_lock_slowpath <- mac80211_hwsim_tx_frame_no_nl <- hrtimer_run_softirq Environment: Kernel: 6.18.0 #1 PREEMPT(full) Arch: x86_64 (QEMU) Please find the full dmesg output below. sched: DL replenish lagged too much rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-...!: (1 GPs behind) idle=e744/1/0x4000000000000000 softirq=75593/75594 fqs=0 rcu: (detected by 1, t=10504 jiffies, g=98817, q=531 ncpus=4) Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 33319 Comm: syz-executor Not tainted 6.18.0 #1 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 RIP: 0010:memory_is_nonzero home/wmy/Fuzzer/third_tool/linux-6.18/mm/kasan/generic.c:114 [inline] RIP: 0010:memory_is_poisoned_n home/wmy/Fuzzer/third_tool/linux-6.18/mm/kasan/generic.c:140 [inline] RIP: 0010:memory_is_poisoned home/wmy/Fuzzer/third_tool/linux-6.18/mm/kasan/generic.c:172 [inline] RIP: 0010:check_region_inline home/wmy/Fuzzer/third_tool/linux-6.18/mm/kasan/generic.c:191 [inline] RIP: 0010:kasan_check_range+0x7e/0x1c0 home/wmy/Fuzzer/third_tool/linux-6.18/mm/kasan/generic.c:200 Code: 4c 8d 54 37 ff 48 89 fd 48 b8 00 00 00 00 00 fc ff df 4d 89 d1 48 c1 ed 03 49 c1 e9 03 48 01 c5 49 01 c1 48 89 e8 49 8d 59 01 <48> 89 da 48 29 ea 48 83 fa 10 0f 8e c0 00 00 00 41 89 eb 41 83 e3 RSP: 0018:ffffc900000079b8 EFLAGS: 00000286 RAX: fffffbfff1e85f50 RBX: fffffbfff1e85f51 RCX: ffffffff8b43f32e RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffffffff8f42fa80 RBP: fffffbfff1e85f50 R08: 0000000000000000 R09: fffffbfff1e85f50 R10: ffffffff8f42fa83 R11: 0000000000000001 R12: 1ffff92000000f3d R13: 0000000000000003 R14: fffffbfff1e85f50 R15: ffffc90000007a18 FS: 0000555572e6d500(0000) GS:ffff8880cf001000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f00657556c0 CR3: 0000000058d74000 CR4: 00000000000006f0 Call Trace: <IRQ> native_queued_spin_lock_slowpath+0xae/0x9c0 debug_spin_lock_before home/wmy/Fuzzer/third_tool/linux-6.18/kernel/locking/spinlock_debug.c:87 [inline] do_raw_spin_lock+0x20d/0x2b0 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/locking/spinlock_debug.c:115 mac80211_hwsim_tx_frame_no_nl.isra.0+0x6f1/0x12c0 mac80211_hwsim_tx_frame+0x1ed/0x2a0 mac80211_hwsim_beacon_tx+0x56d/0x9e0 __iterate_interfaces+0x2e0/0x650 home/wmy/Fuzzer/third_tool/linux-6.18/net/mac80211/util.c:761 ieee80211_iterate_active_interfaces_atomic+0x71/0x1b0 home/wmy/Fuzzer/third_tool/linux-6.18/net/mac80211/util.c:797 mac80211_hwsim_beacon+0x105/0x1b0 __run_hrtimer home/wmy/Fuzzer/third_tool/linux-6.18/kernel/time/hrtimer.c:1779 [inline] __hrtimer_run_queues+0x1f5/0xb30 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/time/hrtimer.c:1841 __hrtimer_get_next_event home/wmy/Fuzzer/third_tool/linux-6.18/kernel/time/hrtimer.c:578 [inline] hrtimer_update_softirq_timer home/wmy/Fuzzer/third_tool/linux-6.18/kernel/time/hrtimer.c:1193 [inline] hrtimer_run_softirq+0x17f/0x350 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/time/hrtimer.c:1861 _test_bit home/wmy/Fuzzer/third_tool/linux-6.18/include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] cpumask_test_cpu home/wmy/Fuzzer/third_tool/linux-6.18/include/linux/cpumask.h:646 [inline] cpu_online home/wmy/Fuzzer/third_tool/linux-6.18/include/linux/cpumask.h:1205 [inline] trace_softirq_exit home/wmy/Fuzzer/third_tool/linux-6.18/include/trace/events/irq.h:142 [inline] handle_softirqs+0x1d4/0x870 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/softirq.c:623 __irq_exit_rcu+0x109/0x170 home/wmy/Fuzzer/third_tool/linux-6.18/arch/x86/include/asm/bitops.h:202 irq_exit_rcu+0x9/0x30 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/softirq.c:738 sysvec_apic_timer_interrupt+0xa8/0xc0 home/wmy/Fuzzer/third_tool/linux-6.18/arch/x86/kernel/apic/apic.c:2145 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x1a/0x20 home/wmy/Fuzzer/third_tool/linux-6.18/arch/x86/include/asm/idtentry.h:697 RIP: 0010:__sanitizer_cov_trace_pc+0x4b/0x80 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/kcov.c:217 Code: 74 1d a9 00 00 0f 00 75 16 a9 00 00 f0 00 74 05 c3 cc cc cc cc 8b 82 7c 16 00 00 85 c0 75 05 e9 5b dc 89 09 8b 82 58 16 00 00 <83> f8 02 75 f0 48 8b 8a 60 16 00 00 8b 92 5c 16 00 00 48 8b 01 48 RSP: 0018:ffffc90002d47698 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff82075ed9 RDX: ffff88802a758000 RSI: ffffffff82075ee7 RDI: 0000000000000007 RBP: dffffc0000000000 R08: 0000000000000001 R09: fffff940002a92c6 R10: 0000000000000000 R11: 0000000000000000 R12: ffffea0001549630 R13: ffffea0001549600 R14: ffffea0001549618 R15: ffffea0001549600 copy_pte_range home/wmy/Fuzzer/third_tool/linux-6.18/mm/memory.c:1284 [inline] copy_pmd_range home/wmy/Fuzzer/third_tool/linux-6.18/mm/memory.c:1390 [inline] copy_pud_range home/wmy/Fuzzer/third_tool/linux-6.18/mm/memory.c:1427 [inline] copy_p4d_range home/wmy/Fuzzer/third_tool/linux-6.18/mm/memory.c:1451 [inline] copy_page_range+0x1c67/0x63a0 home/wmy/Fuzzer/third_tool/linux-6.18/mm/memory.c:1539 rwsem_assert_held_write home/wmy/Fuzzer/third_tool/linux-6.18/include/linux/rwsem.h:215 [inline] mmap_assert_write_locked home/wmy/Fuzzer/third_tool/linux-6.18/include/linux/mmap_lock.h:76 [inline] vma_end_write_all home/wmy/Fuzzer/third_tool/linux-6.18/include/linux/mmap_lock.h:347 [inline] mmap_write_unlock home/wmy/Fuzzer/third_tool/linux-6.18/include/linux/mmap_lock.h:354 [inline] dup_mmap+0xd9e/0x20d0 home/wmy/Fuzzer/third_tool/linux-6.18/mm/mmap.c:1872 futex_init_task home/wmy/Fuzzer/third_tool/linux-6.18/include/linux/futex.h:73 [inline] copy_process+0x36ba/0x76c0 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/fork.c:2230 kernel_clone+0xea/0x8b0 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/fork.c:2609 __do_sys_clone+0xce/0x120 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/fork.c:2750 do_syscall_64+0xcb/0xfa0 home/wmy/Fuzzer/third_tool/linux-6.18/arch/x86/entry/syscall_64.c:99 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f00649a6d07 Code: 00 00 90 f3 0f 1e fa 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 41 41 89 c0 85 c0 75 2c 64 48 8b 04 25 10 00 RSP: 002b:00007ffe2d0a2b98 EFLAGS: 00000246 ORIG_RAX: 0000000000000038 RAX: ffffffffffffffda RBX: 00007f006575d680 RCX: 00007f00649a6d07 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001 R10: 0000555572e6d7d0 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000032 R14: 00007ffe2d0a2d80 R15: 00000000000e717e </TASK> rcu: rcu_preempt kthread starved for 10509 jiffies! g98817 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:28520 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: <TASK> sched_info_arrive home/wmy/Fuzzer/third_tool/linux-6.18/kernel/sched/stats.h:267 [inline] sched_info_switch home/wmy/Fuzzer/third_tool/linux-6.18/kernel/sched/stats.h:330 [inline] prepare_task_switch home/wmy/Fuzzer/third_tool/linux-6.18/kernel/sched/core.c:5122 [inline] context_switch home/wmy/Fuzzer/third_tool/linux-6.18/kernel/sched/core.c:5272 [inline] __schedule+0x1044/0x5bb0 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/sched/core.c:6929 __schedule_loop home/wmy/Fuzzer/third_tool/linux-6.18/kernel/sched/core.c:7011 [inline] schedule+0xe7/0x3a0 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/sched/core.c:7026 schedule_timeout+0x113/0x280 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/time/sleep_timeout.c:98 rcu_gp_fqs_check_wake home/wmy/Fuzzer/third_tool/linux-6.18/kernel/rcu/tree.c:2007 [inline] rcu_gp_fqs_loop+0x18c/0xa00 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/rcu/tree.c:2083 rcu_gp_kthread+0x26f/0x370 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/rcu/tree.c:2280 kthread+0x3d0/0x780 home/wmy/Fuzzer/third_tool/linux-6.18/kernel/kthread.c:463 ret_from_fork+0x676/0x7d0 home/wmy/Fuzzer/third_tool/linux-6.18/arch/x86/kernel/process.c:195 ret_from_fork_asm+0x1a/0x30 home/wmy/Fuzzer/third_tool/linux-6.18/arch/x86/entry/entry_64.S:245 </TASK> Best regards, Zhi Wang
