WARNING in clear_standby

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    46c163a036b4 Add linux-next specific files for 20180921
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17e32b9e400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=20ea07a946ad19d7
dashboard link: https://syzkaller.appspot.com/bug?extid=acdeb633f6211ccdf886
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14ffa12a400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1668561a400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+acdeb633f6211ccdf886@xxxxxxxxxxxxxxxxxxxxxxxxx

libceph: mon0 [::1]:6789 socket error on write
libceph: mon0 [::1]:6789 socket error on write
libceph: mon0 [::1]:6789 socket error on write
libceph: mon0 [::1]:6789 socket error on write
libceph: mon0 [::1]:6789 socket error on write
WARNING: CPU: 1 PID: 5595 at net/ceph/messenger.c:3101  
clear_standby+0x174/0x1b0 net/ceph/messenger.c:3101
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 5595 Comm: syz-executor575 Not tainted  
4.19.0-rc4-next-20180921+ #77
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+0x1d3/0x2c4 lib/dump_stack.c:113
 panic+0x238/0x4e7 kernel/panic.c:184
 __warn.cold.8+0x163/0x1ba kernel/panic.c:536
 report_bug+0x254/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
RIP: 0010:clear_standby+0x174/0x1b0 net/ceph/messenger.c:3101
Code: 48 89 da 48 c7 c6 00 99 e3 88 48 c7 c7 e0 d3 4f 8a e8 a0 ee 02 fc e9  
fe fe ff ff e8 06 e4 21 fa e9 47 ff ff ff e8 7c 6a de f9 <0f> 0b eb 85 4c  
89 ef e8 10 e4 21 fa e9 ae fe ff ff 4c 89 ef e8 03
RSP: 0018:ffff8801bfb67710 EFLAGS: 00010293
RAX: ffff8801d928e5c0 RBX: ffff8801cbca2028 RCX: ffffffff879ee638
RDX: 0000000000000000 RSI: ffffffff879ee6b4 RDI: 0000000000000007
RBP: ffff8801bfb67728 R08: ffff8801d928e5c0 R09: ffffed0039794435
R10: ffff8801bfb67728 R11: ffff8801cbca21af R12: 0000000000000001
R13: ffff8801cbca2160 R14: ffff8801c878fb90 R15: ffff8801bfb67808
 ceph_con_send+0x471/0x930 net/ceph/messenger.c:3136
 __send_prepared_auth_request+0x155/0x1b0 net/ceph/mon_client.c:111
 __open_session+0x3df/0x640 net/ceph/mon_client.c:199
 ceph_monc_open_session+0x47/0x60 net/ceph/mon_client.c:448
 __ceph_open_session+0xe2/0x830 net/ceph/ceph_common.c:705
 ceph_real_mount fs/ceph/super.c:900 [inline]
 ceph_mount+0x1410/0x1ea0 fs/ceph/super.c:1085
 legacy_get_tree+0x131/0x460 fs/fs_context.c:718
 vfs_get_tree+0x1cb/0x5c0 fs/super.c:1795
 do_new_mount fs/namespace.c:2648 [inline]
 do_mount+0x70c/0x1d90 fs/namespace.c:2974
 ksys_mount+0x12d/0x140 fs/namespace.c:3190
 __do_sys_mount fs/namespace.c:3204 [inline]
 __se_sys_mount fs/namespace.c:3201 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3201
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440d39
Code: e8 cc ab 02 00 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 bb 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffdf06babe8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000440d39
RDX: 00000000200001c0 RSI: 0000000020000180 RDI: 0000000020000240
RBP: 0000000000000000 R08: 0000000000000000 R09: 00000009004002c8
R10: 0000000000000000 R11: 0000000000000286 R12: 000000000000956a
R13: 0000000000401d10 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


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