bisecting fixing commit since 20b3a3dfdf6c55b50bbdc8e231a3dbf6bf965dc7 building syzkaller on 70c104a18f3d409bc6dde950b50258d3d280d99b testing commit 20b3a3dfdf6c55b50bbdc8e231a3dbf6bf965dc7 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 762e307bf5d56fc1dafe9862cd45dd725eb5fabc1963e90709be66d7dd08353c run #0: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #1: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #2: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #3: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #4: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #5: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #6: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #7: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #8: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #9: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #10: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #11: crashed: INFO: rcu detected stall in rtnl_newlink run #12: crashed: INFO: rcu detected stall in rtnl_newlink run #13: crashed: INFO: rcu detected stall in rtnl_newlink run #14: crashed: INFO: rcu detected stall in rtnl_newlink run #15: crashed: INFO: rcu detected stall in rtnl_newlink run #16: crashed: INFO: rcu detected stall in rtnl_newlink run #17: crashed: INFO: rcu detected stall in rtnl_newlink run #18: crashed: INFO: rcu detected stall in rtnl_newlink run #19: crashed: INFO: rcu detected stall in rtnl_newlink testing current HEAD e23d55af0e1fca9be5c99f0c37d48b289f4d6489 testing commit e23d55af0e1fca9be5c99f0c37d48b289f4d6489 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: c78e4845bf554e0233a6b041aa80ed4ac17c98622c01cffb893b87f364d0640f run #0: crashed: BUG: unable to handle kernel paging request in __alloc_skb run #1: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #2: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #3: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #4: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #5: crashed: BUG: soft lockup in batadv_iv_send_outstanding_bat_ogm_packet run #6: crashed: INFO: rcu detected stall in rtnl_newlink run #7: crashed: INFO: rcu detected stall in rtnl_newlink run #8: crashed: INFO: rcu detected stall in rtnl_newlink run #9: crashed: INFO: rcu detected stall in rtnl_newlink revisions tested: 2, total time: 31m22.932921862s (build: 20m41.834875913s, test: 10m7.823297495s) the crash still happens on HEAD commit msg: Linux 4.19.205 crash: INFO: rcu detected stall in rtnl_newlink batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 1-...!: (10499 ticks this GP) idle=34a/1/0x4000000000000002 softirq=9600/9600 fqs=0 rcu: (t=10502 jiffies g=4853 q=1596) rcu: rcu_preempt kthread starved for 10503 jiffies! g4853 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1 rcu: RCU grace-period kthread stack dump: rcu_preempt I29160 10 2 0x80000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x398/0xd20 kernel/time/timer.c:1818 rcu_gp_kthread+0xd2b/0x23e0 kernel/rcu/tree.c:2202 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 NMI backtrace for cpu 1 CPU: 1 PID: 7153 Comm: syz-executor.3 Not tainted 4.19.205-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x17c/0x226 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xf5/0x120 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1340 print_cpu_stall kernel/rcu/tree.c:1478 [inline] check_cpu_stall kernel/rcu/tree.c:1550 [inline] __rcu_pending kernel/rcu/tree.c:3293 [inline] rcu_pending kernel/rcu/tree.c:3336 [inline] rcu_check_callbacks.cold.62+0x5b1/0xd89 kernel/rcu/tree.c:2682 update_process_times+0x2a/0x60 kernel/time/timer.c:1650 tick_sched_handle.isra.5+0x6b/0x130 kernel/time/tick-sched.c:168 tick_sched_timer+0x3c/0xf0 kernel/time/tick-sched.c:1278 __run_hrtimer kernel/time/hrtimer.c:1419 [inline] __hrtimer_run_queues+0x2fa/0xaa0 kernel/time/hrtimer.c:1481 hrtimer_interrupt+0x2e2/0x760 kernel/time/hrtimer.c:1539 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1071 [inline] smp_apic_timer_interrupt+0x114/0x540 arch/x86/kernel/apic/apic.c:1096 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline] RIP: 0010:lock_acquire+0x1f5/0x3a0 kernel/locking/lockdep.c:3911 Code: 00 00 00 00 00 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 99 01 00 00 48 83 3d 1f 42 07 07 00 0f 84 1c 01 00 00 48 8b 7d c0 57 9d <0f> 1f 44 00 00 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 65 8b RSP: 0018:ffff8881da7deb18 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13 RAX: dffffc0000000000 RBX: ffff8881dab904c0 RCX: 1ffff1103b5721b7 RDX: 1ffffffff10a3f81 RSI: 0000000000000000 RDI: 0000000000000286 RBP: ffff8881da7deb60 R08: 0000000000007ff5 R09: ffffffff89cad828 R10: ffff8881dab90d98 R11: 0000000000000001 R12: 0000000000000000 R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881dab904c0 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168 spin_lock_bh include/linux/spinlock.h:334 [inline] batadv_tt_local_purge+0xe7/0x2c0 net/batman-adv/translation-table.c:1454 batadv_tt_local_resize_to_mtu+0x87/0xf0 net/batman-adv/translation-table.c:4207 batadv_update_min_mtu net/batman-adv/hard-interface.c:637 [inline] batadv_hardif_activate_interface.part.3.cold.8+0xcb/0x313 net/batman-adv/hard-interface.c:664 batadv_hardif_activate_interface net/batman-adv/hard-interface.c:825 [inline] batadv_hardif_enable_interface+0x987/0xa40 net/batman-adv/hard-interface.c:817 batadv_softif_slave_add+0x7f/0xd0 net/batman-adv/soft-interface.c:898 do_set_master net/core/rtnetlink.c:2321 [inline] do_set_master+0x171/0x200 net/core/rtnetlink.c:2295 do_setlink+0x94c/0x2ec0 net/core/rtnetlink.c:2455 rtnl_newlink+0x975/0x1360 net/core/rtnetlink.c:3077 rtnetlink_rcv_msg+0x34f/0x950 net/core/rtnetlink.c:4782 netlink_rcv_skb+0x13e/0x3d0 net/netlink/af_netlink.c:2457 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4800 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1911 sock_sendmsg_nosec net/socket.c:651 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:661 ___sys_sendmsg+0x647/0x950 net/socket.c:2225 __sys_sendmsg+0xd9/0x180 net/socket.c:2263 __do_sys_sendmsg net/socket.c:2272 [inline] __se_sys_sendmsg net/socket.c:2270 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2270 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x463b49 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f2232c15188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000055bf00 RCX: 0000000000463b49 RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000004 RBP: 00000000004ae538 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf00 R13: 00007ffe8fe1bdaf R14: 00007f2232c15300 R15: 0000000000022000 net_ratelimit: 6028 callbacks suppressed batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) net_ratelimit: 6268 callbacks suppressed batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-224) ---------------- Code disassembly (best guess): 0: 00 00 add %al,(%rax) 2: 00 00 add %al,(%rax) 4: 00 48 89 add %cl,-0x77(%rax) 7: fa cli 8: 48 c1 ea 03 shr $0x3,%rdx c: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) 10: 0f 85 99 01 00 00 jne 0x1af 16: 48 83 3d 1f 42 07 07 cmpq $0x0,0x707421f(%rip) # 0x707423d 1d: 00 1e: 0f 84 1c 01 00 00 je 0x140 24: 48 8b 7d c0 mov -0x40(%rbp),%rdi 28: 57 push %rdi 29: 9d popfq * 2a: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) <-- trapping instruction 2f: 48 8d 65 d8 lea -0x28(%rbp),%rsp 33: 5b pop %rbx 34: 41 5c pop %r12 36: 41 5d pop %r13 38: 41 5e pop %r14 3a: 41 5f pop %r15 3c: 5d pop %rbp 3d: c3 retq 3e: 65 gs 3f: 8b .byte 0x8b