Subject: Re: divide error in ___bpf_prog_run
To: syzbot <syzbot+48340bb518e88849e2e3@syzkaller.appspotmail.com>,
        ast@kernel.org, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com
References: <001a11405130ff1e9705629eb53c@google.com>
From: Daniel Borkmann <daniel@iogearbox.net>
Message-ID: <4b1402b3-cb48-e625-23d5-c2c83df34815@iogearbox.net>
Date: Sun, 14 Jan 2018 01:16:17 +0100
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On 01/13/2018 02:58 AM, syzbot wrote:
> Hello,
> 
> syzkaller hit the following crash on 19d28fbd306e7ae7c1acf05c3e6968b56f0d196b
> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers

Fixed by:

http://patchwork.ozlabs.org/patch/860270/
http://patchwork.ozlabs.org/patch/860275/

Will get them in as soon as DaveM pulled the current batch into net.

> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+48340bb518e88849e2e3@syzkaller.appspotmail.com
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> 
> divide error: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 0 PID: 3501 Comm: syzkaller702501 Not tainted 4.15.0-rc7+ #185
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:___bpf_prog_run+0x3cc7/0x6100 kernel/bpf/core.c:976
> RSP: 0018:ffff8801c7927200 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffc90000002030 RDI: ffffc90000002049
> RBP: ffff8801c7927308 R08: 1ffff10038f24dd9 R09: 0000000000000002
> R10: ffff8801c7927388 R11: 0000000000000000 R12: ffff8801c7927340
> R13: ffffc90000002048 R14: ffff8801c7927340 R15: 00000000fffffffc
> FS:  0000000002255880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020fd3000 CR3: 00000001c2284004 CR4: 00000000001606f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  __bpf_prog_run160+0xde/0x150 kernel/bpf/core.c:1346
>  bpf_prog_run_save_cb include/linux/filter.h:556 [inline]
>  sk_filter_trim_cap+0x33c/0x9c0 net/core/filter.c:103
>  sk_filter include/linux/filter.h:685 [inline]
>  netlink_unicast+0x1b8/0x6b0 net/netlink/af_netlink.c:1336
>  nlmsg_unicast include/net/netlink.h:608 [inline]
>  rtnl_unicast net/core/rtnetlink.c:700 [inline]
>  rtnl_stats_get+0x7bb/0xa10 net/core/rtnetlink.c:4363
>  rtnetlink_rcv_msg+0x57f/0xb10 net/core/rtnetlink.c:4530
>  netlink_rcv_skb+0x224/0x470 net/netlink/af_netlink.c:2441
>  rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4548
>  netlink_unicast_kernel net/netlink/af_netlink.c:1308 [inline]
>  netlink_unicast+0x4c4/0x6b0 net/netlink/af_netlink.c:1334
>  netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1897
>  sock_sendmsg_nosec net/socket.c:630 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:640
>  sock_write_iter+0x31a/0x5d0 net/socket.c:909
>  call_write_iter include/linux/fs.h:1772 [inline]
>  new_sync_write fs/read_write.c:469 [inline]
>  __vfs_write+0x684/0x970 fs/read_write.c:482
>  vfs_write+0x189/0x510 fs/read_write.c:544
>  SYSC_write fs/read_write.c:589 [inline]
>  SyS_write+0xef/0x220 fs/read_write.c:581
>  entry_SYSCALL_64_fastpath+0x23/0x9a
> RIP: 0033:0x43ffc9
> RSP: 002b:00007ffe602ec9f8 EFLAGS: 00000217 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 000000000043ffc9
> RDX: 0000000000000026 RSI: 0000000020fd3000 RDI: 0000000000000004
> RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000004 R11: 0000000000000217 R12: 0000000000401930
> R13: 00000000004019c0 R14: 0000000000000000 R15: 0000000000000000
> Code: 89 85 58 ff ff ff 41 0f b6 55 01 c0 ea 04 0f b6 d2 4d 8d 34 d4 4c 89 f2 48 c1 ea 03 80 3c 1a 00 0f 85 ee 1e 00 00 41 8b 0e 31 d2 <48> f7 f1 48 89 85 58 ff ff ff 41 0f b6 45 01 83 e0 0f 4d 8d 34
> RIP: ___bpf_prog_run+0x3cc7/0x6100 kernel/bpf/core.c:976 RSP: ffff8801c7927200
> ---[ end trace 274313e5f69f4eff ]---
> 
> 
> ---
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