Subject: general protection fault in ip6_dst_hoplimit

From: syzbot <[email-masked]>
Date: Tue, 19 Mar 2019 02:22:05 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    d9862cfb Merge tag 'mips_5.1' of git://git.kernel.org/pub/..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12747c93200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=73d88a42238825ad
dashboard link: https://syzkaller.appspot.com/bug?extid=4c869fc20129562c53fa
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

dst_release: dst:00000000f3b89511 refcnt:-2120685656
dst_release: dst:00000000f3b89511 refcnt:-2120685656
IPVS: set_ctl: invalid protocol: 46 0.0.4.1:20003
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 14303 Comm: syz-executor.2 Not tainted 5.0.0+ #97
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:ip6_dst_hoplimit+0x26/0x3f0 net/ipv6/output_core.c:127
Code: 00 00 00 00 55 48 89 e5 41 55 41 54 53 48 89 fb e8 0f 2e 4b fb 48 8d  
7b 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 7d 03 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b
RSP: 0018:ffff888029bb77c8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000004a58 RCX: ffffc9000a21d000
RDX: 000000000000094d RSI: ffffffff86248861 RDI: 0000000000004a68
RBP: ffff888029bb77e0 R08: ffff888096e1e400 R09: ffffed1015d25021
R10: ffffed1015d25bcf R11: ffff8880ae928107 R12: ffff888064f31880
R13: 0000000000004a58 R14: 0000000000000000 R15: ffff888029bb7e20
FS:  00007f66dbd52700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5833499000 CR3: 000000009ae87000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  ip6_sk_dst_hoplimit include/net/ipv6.h:765 [inline]
  udpv6_sendmsg+0x23af/0x28d0 net/ipv6/udp.c:1459
  inet_sendmsg+0x147/0x5d0 net/ipv4/af_inet.c:798
  sock_sendmsg_nosec net/socket.c:622 [inline]
  sock_sendmsg+0xdd/0x130 net/socket.c:632
  ___sys_sendmsg+0x806/0x930 net/socket.c:2137
  __sys_sendmsg+0x105/0x1d0 net/socket.c:2175
  __do_sys_sendmsg net/socket.c:2184 [inline]
  __se_sys_sendmsg net/socket.c:2182 [inline]
  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2182
  do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
kobject: 'loop5' (000000000bae834e): kobject_uevent_env
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458079
Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f66dbd51c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
kobject: 'loop5' (000000000bae834e): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458079
RDX: 0000000000000000 RSI: 0000000020002b80 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f66dbd526d4
R13: 00000000004c5601 R14: 00000000004d94a8 R15: 00000000ffffffff
Modules linked in:
kobject: 'loop4' (0000000057f28e01): kobject_uevent_env
---[ end trace ad1e9a18c63dc6fd ]---
kobject: 'ip6gre0' (00000000482f98f6): kobject_cleanup, parent            
(null)
RIP: 0010:ip6_dst_hoplimit+0x26/0x3f0 net/ipv6/output_core.c:127
kobject: 'loop4' (0000000057f28e01): fill_kobj_path: path  
= '/devices/virtual/block/loop4'
Code: 00 00 00 00 55 48 89 e5 41 55 41 54 53 48 89 fb e8 0f 2e 4b fb 48 8d  
7b 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 7d 03 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b
kobject: 'ip6gre0' (00000000482f98f6): auto cleanup 'remove' event
RSP: 0018:ffff888029bb77c8 EFLAGS: 00010206
kobject: 'loop3' (000000006d432d43): kobject_uevent_env
RAX: dffffc0000000000 RBX: 0000000000004a58 RCX: ffffc9000a21d000
kobject: 'ip6gre0' (00000000482f98f6): kobject_uevent_env
RDX: 000000000000094d RSI: ffffffff86248861 RDI: 0000000000004a68
kobject: 'loop3' (000000006d432d43): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
RBP: ffff888029bb77e0 R08: ffff888096e1e400 R09: ffffed1015d25021
kobject: 'ip6gre0' (00000000482f98f6): kobject_uevent_env: uevent_suppress  
caused the event to drop!
R10: ffffed1015d25bcf R11: ffff8880ae928107 R12: ffff888064f31880
kobject: 'ip6gre0' (00000000482f98f6): calling ktype release
R13: 0000000000004a58 R14: 0000000000000000 R15: ffff888029bb7e20
kobject: 'ip6gre0': free name
FS:  00007f66dbd52700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000625208 CR3: 000000009ae87000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
kobject: 'rx-0' (00000000e6299323): kobject_cleanup, parent 000000006ae1d517
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email-masked].

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.