Re: general protection fault in ip6_dst_hoplimit

[Dmitry Vyukov]

On Tue, Mar 19, 2019 at 10:22 AM syzbot
<syzbot+4c869fc20129562c53fa@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> 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: syzbot+4c869fc20129562c53fa@xxxxxxxxxxxxxxxxxxxxxxxxx


Eric, searching the dashboard for "ip6_dst" I've also found this. Can
this be fixed by your "ipv6: fix races in ip6_dst_destroy()"?
https://patchwork.ozlabs.org/patch/1092328/
If there is some chance that it is fixed by your patch, then it may be
better to mark it as fixed because there does not seem to be any other
hypothesis.


> 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 syzkaller@xxxxxxxxxxxxxxxxx
>
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