bisecting fixing commit since 4520f06b03ae667e442da1ab9351fd28cd7ac598
building syzkaller on a8c6a3f8da30ccf825c6001c81a8adff21829c30
testing commit 4520f06b03ae667e442da1ab9351fd28cd7ac598 with gcc (GCC) 8.1.0
kernel signature: ac848fe135f69be50027a7ca3cd0be08d8bfbb09d81df6b2c231cb0245f5db38
run #0: crashed: WARNING in kcm_write_msgs
run #1: crashed: WARNING in kcm_write_msgs
run #2: crashed: WARNING in kcm_write_msgs
run #3: crashed: WARNING in kcm_write_msgs
run #4: crashed: WARNING in kcm_write_msgs
run #5: crashed: WARNING in kcm_write_msgs
run #6: crashed: WARNING in kcm_write_msgs
run #7: crashed: WARNING in kcm_write_msgs
run #8: crashed: WARNING in kcm_write_msgs
run #9: crashed: WARNING in corrupted
testing current HEAD ab9dfda232481dcfaf549ce774004d116fc80c13
testing commit ab9dfda232481dcfaf549ce774004d116fc80c13 with gcc (GCC) 8.1.0
kernel signature: c66a63e613f6f8461d08e5100f1af1e41461cb18dcfda862b0498c355ead73d1
run #0: crashed: WARNING in kcm_write_msgs
run #1: crashed: WARNING in kcm_write_msgs
run #2: crashed: WARNING in kcm_write_msgs
run #3: crashed: WARNING in corrupted
run #4: crashed: WARNING in kcm_write_msgs
run #5: crashed: WARNING in kcm_write_msgs
run #6: crashed: WARNING in kcm_write_msgs
run #7: crashed: WARNING in kcm_write_msgs
run #8: crashed: WARNING in kcm_write_msgs
run #9: crashed: WARNING in kcm_write_msgs
revisions tested: 2, total time: 26m16.501044952s (build: 18m8.904078527s, test: 6m55.260963076s)
the crash still happens on HEAD
commit msg: Linux 4.14.180
crash: WARNING in kcm_write_msgs
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_virt_wifi: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_virt_wifi: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): veth0_macvtap: link is not ready
IPv6: ADDRCONF(NETDEV_UP): veth1_macvtap: link is not ready
------------[ cut here ]------------
WARNING: CPU: 1 PID: 7826 at net/kcm/kcmsock.c:629 kcm_write_msgs+0xddd/0x1660 net/kcm/kcmsock.c:662
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_macvtap: link becomes ready
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 7826 Comm: syz-executor.4 Not tainted 4.14.180-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_macvtap: link becomes ready
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xf7/0x13b lib/dump_stack.c:58
 panic+0x1b0/0x358 kernel/panic.c:183
 __warn.cold.8+0x25/0x2c kernel/panic.c:547
device veth0_macvtap entered promiscuous mode
 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
IPv6: ADDRCONF(NETDEV_UP): macvtap0: link is not ready
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:963
RIP: 0010:kcm_write_msgs+0xddd/0x1660 net/kcm/kcmsock.c:629
RSP: 0018:ffff8880a8d2f8f8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8880889b6840 RCX: 0000000000000002
device veth1_macvtap entered promiscuous mode
RDX: 0000000000008000 RSI: 0000000000000000 RDI: ffff8880889b6842
RBP: ffff8880a8d2f9b8 R08: ffff8880a144cf28 R09: 0000000000000000
R10: ffff8880a9f80680 R11: 0000000000000000 R12: 00000000000000c0
R13: ffff8880a52430c0 R14: ffff8880889b6780 R15: ffff8880880a0080
 kcm_sendmsg+0x183d/0x2580 net/kcm/kcmsock.c:1035
IPv6: ADDRCONF(NETDEV_UP): macsec0: link is not ready
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0xf0 net/socket.c:656
 sock_write_iter+0x20d/0x400 net/socket.c:925
IPv6: ADDRCONF(NETDEV_UP): veth0_to_batadv: link is not ready
 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
IPv6: ADDRCONF(NETDEV_UP): veth1_to_batadv: link is not ready
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
 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: 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+0x42/0xb7
RIP: 0033:0x45c889
RSP: 002b:00007f041b8c6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
RAX: ffffffffffffffda RBX: 00007f041b8c76d4 RCX: 000000000045c889
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000c4c R14: 00000000004ca0ad R15: 000000000076bf0c
Kernel Offset: disabled
Rebooting in 86400 seconds..