bisecting fixing commit since 4520f06b03ae667e442da1ab9351fd28cd7ac598
building syzkaller on a8c6a3f8da30ccf825c6001c81a8adff21829c30
testing commit 4520f06b03ae667e442da1ab9351fd28cd7ac598 with gcc (GCC) 8.1.0
kernel signature: 5e7f941188116f91b36a5be634f57b3f8a9b7ed13d96a9be98f1cd5a0613a8ea
all runs: crashed: WARNING in kcm_write_msgs
testing current HEAD c6db52a88798e5a0dfef80041ad4d33cc8cf04eb
testing commit c6db52a88798e5a0dfef80041ad4d33cc8cf04eb with gcc (GCC) 8.1.0
kernel signature: babf3aaf82bd17f38a1e9eb9211a63755661c15b03588903add6101b6a4aa58d
all runs: crashed: WARNING in kcm_write_msgs
revisions tested: 2, total time: 23m50.594085009s (build: 16m55.514581191s, test: 6m14.352361252s)
the crash still happens on HEAD
commit msg: Linux 4.14.183
crash: WARNING in kcm_write_msgs
IPv6: ADDRCONF(NETDEV_UP): batadv_slave_1: link is not ready
batman_adv: batadv0: Interface activated: batadv_slave_1
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
------------[ cut here ]------------
WARNING: CPU: 1 PID: 8032 at net/kcm/kcmsock.c:629 kcm_write_msgs+0xddd/0x1660 net/kcm/kcmsock.c:662
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 8032 Comm: syz-executor.4 Not tainted 4.14.183-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
 __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
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964
RIP: 0010:kcm_write_msgs+0xddd/0x1660 net/kcm/kcmsock.c:629
RSP: 0018:ffff88809802f8f8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8880a0d8b680 RCX: 0000000000000002
RDX: 0000000000008000 RSI: 0000000000000000 RDI: ffff8880a0d8b682
RBP: ffff88809802f9b8 R08: ffff88809b30cf68 R09: 0000000000000000
R10: ffff8880943f3480 R11: 0000000000000000 R12: 00000000000000c0
R13: ffff888086258ec0 R14: ffff8880a0d8b5c0 R15: ffff88809e9d3380
 kcm_sendmsg+0x183d/0x2580 net/kcm/kcmsock.c:1035
 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
 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
 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
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45c889
RSP: 002b:00007f2b1315cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2b1315d6d4 RCX: 000000000045c889
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 000000000076bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000c4c R14: 00000000004ca0ad R15: 000000000076bfac
Kernel Offset: disabled
Rebooting in 86400 seconds..