WARNING in kcm_write_msgs

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 54b4fa6d Linux 4.19.113
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=149f2a93e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7b1a0bc5526ebc49
dashboard link: https://syzkaller.appspot.com/bug?extid=c94d23ea2ec93cf2df7e
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16a0f37be00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=132932dbe00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c94d23...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 8437 at net/kcm/kcmsock.c:629 kcm_write_msgs.cold+0x10f/0x13b net/kcm/kcmsock.c:629
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 8437 Comm: syz-executor043 Not tainted 4.19.113-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+0x188/0x20d lib/dump_stack.c:118
panic+0x26a/0x50e kernel/panic.c:186
__warn.cold+0x20/0x46 kernel/panic.c:541
report_bug+0x262/0x2a0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x1d7/0x310 arch/x86/kernel/traps.c:296
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1037
RIP: 0010:kcm_write_msgs.cold+0x10f/0x13b net/kcm/kcmsock.c:629
Code: c7 44 24 58 00 00 00 00 48 8b 80 50 02 00 00 48 89 44 24 28 e9 2d b6 ff ff e8 b3 65 de fa 48 c7 c7 80 bd 1c 88 e8 c0 84 c9 fa <0f> 0b 8b 44 24 70 bb ea ff ff ff 89 44 24 58 e9 7d b7 ff ff e8 8e
RSP: 0018:ffff88807cebf980 EFLAGS: 00010286
RAX: 0000000000000024 RBX: 0000000000008000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8152d3a1 RDI: ffffed100f9d7f22
RBP: ffff88808cafe100 R08: 0000000000000024 R09: ffffed1015cc5079
R10: ffffed1015cc5078 R11: ffff8880ae6283c7 R12: ffff88808cafe040
R13: ffff8880a8707400 R14: 00000000000000c0 R15: 0000000000000000
kcm_sendmsg+0x1b68/0x212a net/kcm/kcmsock.c:1035
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:632
sock_write_iter+0x283/0x3c0 net/socket.c:901
call_write_iter include/linux/fs.h:1821 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x512/0x760 fs/read_write.c:487
vfs_write+0x206/0x550 fs/read_write.c:549
ksys_write+0x12b/0x2a0 fs/read_write.c:599
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446fe9
Code: e8 dc e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 2b 06 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f5540447d98 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006dcc48 RCX: 0000000000446fe9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00000000006dcc40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc4c
R13: 00000000200003c0 R14: 00000000004af5c8 R15: 000000000000d4f5
Kernel Offset: disabled
Rebooting in 86400 seconds..


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