bisecting fixing commit since c10b57a567e4333b9fdf60b5ec36de9859263ca2 building syzkaller on 3f3c557402456696073f79aafa65b4d7fa2b8794 testing commit c10b57a567e4333b9fdf60b5ec36de9859263ca2 with gcc (GCC) 8.1.0 kernel signature: 65c236ed4238369ff4e17ee821ce8ce02b4d910124d22fa1053f230adee2e959 run #0: crashed: WARNING in ip_rt_bug run #1: crashed: WARNING in ip_rt_bug run #2: crashed: WARNING in ip_rt_bug run #3: crashed: WARNING in corrupted run #4: crashed: WARNING in ip_rt_bug run #5: crashed: WARNING in ip_rt_bug run #6: crashed: WARNING in ip_rt_bug run #7: crashed: WARNING in ip_rt_bug run #8: crashed: WARNING in ip_rt_bug run #9: crashed: WARNING in corrupted testing current HEAD b850307b279cbd12ab8c654d1a3dfe55319cc475 testing commit b850307b279cbd12ab8c654d1a3dfe55319cc475 with gcc (GCC) 8.1.0 kernel signature: d7d423fb0f7712209cdab85a74a4376111fed0c77f4012d34d44751d2d5ee9ac run #0: crashed: WARNING in ip_rt_bug run #1: crashed: WARNING in corrupted run #2: crashed: WARNING in ip_rt_bug run #3: crashed: WARNING in ip_rt_bug run #4: crashed: WARNING in ip_rt_bug run #5: crashed: WARNING in ip_rt_bug run #6: crashed: WARNING in ip_rt_bug run #7: crashed: WARNING in ip_rt_bug run #8: crashed: WARNING in ip_rt_bug run #9: crashed: WARNING in ip_rt_bug revisions tested: 2, total time: 22m55.982809128s (build: 16m22.98694392s, test: 6m8.527226369s) the crash still happens on HEAD commit msg: Linux 4.14.184 crash: WARNING in ip_rt_bug IPv6: ADDRCONF(NETDEV_CHANGE): macvtap0: link becomes ready device veth1_macvtap entered promiscuous mode IPv6: ADDRCONF(NETDEV_UP): veth0_to_batadv: link is not ready ------------[ cut here ]------------ IPv6: ADDRCONF(NETDEV_UP): veth1_to_batadv: link is not ready WARNING: CPU: 1 PID: 7805 at net/ipv4/route.c:1240 ip_rt_bug+0xc/0x20 net/ipv4/route.c:1239 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 7805 Comm: syz-executor.5 Not tainted 4.14.184-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 panic+0x1b0/0x358 kernel/panic.c:183 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 __warn.cold.8+0x25/0x2c kernel/panic.c:547 report_bug+0x1a4/0x1f3 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:177 [inline] do_error_trap+0x1bd/0x310 arch/x86/kernel/traps.c:295 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964 RIP: 0010:ip_rt_bug+0xc/0x20 net/ipv4/route.c:1240 RSP: 0018:ffff88808d6df0f8 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffff8880a9be96c0 RCX: 0000000000000000 RDX: 1ffffffff0fe2cf1 RSI: ffffffff87f83e60 RDI: 0000000000000286 RBP: ffff88808d6df0f8 R08: ffff888088c66ef8 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880940b8080 R13: ffff88808b1497c0 R14: ffff8880a9be9718 R15: ffff88808d6df394 dst_output include/net/dst.h:462 [inline] ip_local_out+0x78/0x130 net/ipv4/ip_output.c:124 ip_send_skb+0x36/0xa0 net/ipv4/ip_output.c:1422 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! ip_push_pending_frames+0x4d/0x70 net/ipv4/ip_output.c:1442 icmp_push_reply+0x356/0x5e0 net/ipv4/icmp.c:395 __icmp_send+0x9f4/0x18f0 net/ipv4/icmp.c:743 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! icmp_send include/net/icmp.h:47 [inline] ip_options_compile+0x9f/0xb0 net/ipv4/ip_options.c:485 ip_rcv_options net/ipv4/ip_input.c:283 [inline] ip_rcv_finish+0x5e7/0x1950 net/ipv4/ip_input.c:364 NF_HOOK include/linux/netfilter.h:250 [inline] ip_rcv+0xb43/0x133d net/ipv4/ip_input.c:493 __netif_receive_skb_core+0x1d54/0x3260 net/core/dev.c:4478 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! __netif_receive_skb+0x1f/0x1b0 net/core/dev.c:4516 netif_receive_skb_internal+0xcc/0x4d0 net/core/dev.c:4589 IPv6: ADDRCONF(NETDEV_UP): batadv_slave_0: link is not ready netif_receive_skb+0x37/0x230 net/core/dev.c:4613 tun_rx_batched.isra.48+0x4b8/0x990 drivers/net/tun.c:1221 batman_adv: batadv0: Interface activated: batadv_slave_0 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 tun_get_user+0xa97/0x3830 drivers/net/tun.c:1581 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! tun_chr_write_iter+0xcb/0x18b drivers/net/tun.c:1608 call_write_iter include/linux/fs.h:1778 [inline] new_sync_write fs/read_write.c:469 [inline] __vfs_write+0x413/0x840 fs/read_write.c:482 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! vfs_write+0x150/0x4f0 fs/read_write.c:544 SYSC_write fs/read_write.c:590 [inline] SyS_write+0x100/0x250 fs/read_write.c:582 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x45c889 RSP: 002b:00007fc5296dfc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fc5296e06d4 RCX: 000000000045c889 RDX: 000000000000100c RSI: 0000000020000240 RDI: 0000000000000005 RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1 R13: 0000000000000d0f R14: 00000000004cf3e1 R15: 000000000076bf0c batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! Kernel Offset: disabled Rebooting in 86400 seconds..