bisecting fixing commit since 20b3a3dfdf6c55b50bbdc8e231a3dbf6bf965dc7 building syzkaller on 70c104a18f3d409bc6dde950b50258d3d280d99b testing commit 20b3a3dfdf6c55b50bbdc8e231a3dbf6bf965dc7 with gcc (GCC) 8.1.0 kernel signature: 8b5320a55abc672241913fe610522a62e367d74cc832d7710b838821f97f83c6 run #0: crashed: BUG: unable to handle kernel paging request in __alloc_skb run #1: crashed: INFO: rcu detected stall in rtnl_newlink run #2: crashed: INFO: rcu detected stall in rtnl_newlink run #3: crashed: INFO: rcu detected stall in rtnl_newlink run #4: crashed: INFO: rcu detected stall in rtnl_newlink run #5: crashed: INFO: rcu detected stall in rtnl_newlink 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 testing current HEAD 13d2ce42de8cb98ff952f8de6307f896203854c2 testing commit 13d2ce42de8cb98ff952f8de6307f896203854c2 with gcc (GCC) 8.1.0 kernel signature: 9037f387ee622ae8cdef94786a6c75a68ba1c2f75820e8229583989545bc328a run #0: crashed: BUG: unable to handle kernel paging request in __alloc_skb run #1: crashed: INFO: rcu detected stall in rtnl_newlink run #2: crashed: INFO: rcu detected stall in rtnl_newlink run #3: crashed: INFO: rcu detected stall in rtnl_newlink run #4: crashed: INFO: rcu detected stall in rtnl_newlink run #5: crashed: INFO: rcu detected stall in rtnl_newlink 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: 28m0.182523317s (build: 18m24.605978135s, test: 8m53.445960804s) the crash still happens on HEAD commit msg: Linux 4.19.163 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-....: (1 GPs behind) idle=87e/1/0x4000000000000002 softirq=7953/7959 fqs=5250 rcu: (t=10502 jiffies g=4889 q=957) NMI backtrace for cpu 1 CPU: 1 PID: 7211 Comm: syz-executor.3 Not tainted 4.19.163-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/0x22a lib/dump_stack.c:118 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xf5/0x119 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+0x5cc/0xd67 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:1401 [inline] __hrtimer_run_queues+0x2fa/0xaa0 kernel/time/hrtimer.c:1463 hrtimer_interrupt+0x2df/0x760 kernel/time/hrtimer.c:1521 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1067 [inline] smp_apic_timer_interrupt+0x114/0x540 arch/x86/kernel/apic/apic.c:1092 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894 RIP: 0010:memory_is_nonzero mm/kasan/kasan.c:183 [inline] RIP: 0010:memory_is_poisoned_n mm/kasan/kasan.c:210 [inline] RIP: 0010:memory_is_poisoned mm/kasan/kasan.c:241 [inline] RIP: 0010:check_memory_region_inline mm/kasan/kasan.c:257 [inline] RIP: 0010:check_memory_region+0x55/0x1b0 mm/kasan/kasan.c:267 Code: 37 ff 48 89 fb 49 b9 00 00 00 00 00 fc ff df 4d 89 da 48 c1 eb 03 49 c1 ea 03 4d 01 ca 49 01 d9 4d 8d 62 01 4c 89 c8 4d 89 e0 <4d> 29 c8 49 83 f8 10 0f 8e 9a 00 00 00 44 89 cb 83 e3 07 75 5a 4d RSP: 0018:ffff8881db9f6b28 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13 RAX: ffffed103984945b RBX: 1ffff1103984945b RCX: ffffffff814caeb4 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8881cc24a2d8 RBP: ffff8881db9f6b40 R08: ffffed103984945c R09: ffffed103984945b R10: ffffed103984945b R11: ffff8881cc24a2db R12: ffffed103984945c R13: ffff8881e7932368 R14: ffff8881e2d95c18 R15: ffff8881eca15f40 kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272 atomic_read include/asm-generic/atomic-instrumented.h:21 [inline] queued_spin_is_locked include/asm-generic/qspinlock.h:35 [inline] debug_spin_unlock kernel/locking/spinlock_debug.c:98 [inline] do_raw_spin_unlock+0x54/0x260 kernel/locking/spinlock_debug.c:134 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:175 [inline] _raw_spin_unlock_bh+0x22/0x40 kernel/locking/spinlock.c:200 spin_unlock_bh include/linux/spinlock.h:374 [inline] batadv_tt_local_purge+0x1f1/0x2c0 net/batman-adv/translation-table.c:1454 batadv_tt_local_resize_to_mtu+0x87/0xf0 net/batman-adv/translation-table.c:4205 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+0x171/0x200 net/core/rtnetlink.c:2321 do_setlink+0x94c/0x2ec0 net/core/rtnetlink.c:2455 rtnl_newlink+0xa1d/0x1320 net/core/rtnetlink.c:3077 rtnetlink_rcv_msg+0x34f/0x950 net/core/rtnetlink.c:4778 netlink_rcv_skb+0x13e/0x3d0 net/netlink/af_netlink.c:2455 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4796 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x666/0xc50 net/netlink/af_netlink.c:1909 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:632 ___sys_sendmsg+0x647/0x950 net/socket.c:2115 __sys_sendmsg+0xd9/0x180 net/socket.c:2153 __do_sys_sendmsg net/socket.c:2162 [inline] __se_sys_sendmsg net/socket.c:2160 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c1f9 Code: 8d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 5b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ff52cd4dc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000002b580 RCX: 000000000045c1f9 RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000004 RBP: 000000000078bf40 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c R13: 00007ffc2b52056f R14: 00007ff52cd4e9c0 R15: 000000000078bf0c net_ratelimit: 6167 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: 6315 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)