Message-ID: <CACT4Y+YwB=hbVjp9i8z1hib015QSurpLu9nX9815TJ-t4e6WVQ@mail.gmail.com>
Date:   Fri, 29 May 2020 08:38:26 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Andrii Nakryiko <andriin@...com>
Cc:     syzbot <syzbot+3610d489778b57cc8031@...kaller.appspotmail.com>,
        Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>, guro@...com,
        kuba@...nel.org, Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: general protection fault in inet_unhash

On Fri, May 29, 2020 at 8:33 AM Andrii Nakryiko <andriin@...com> wrote:
>
> On 5/28/20 11:23 PM, Dmitry Vyukov wrote:
> > On Thu, May 28, 2020 at 11:01 PM 'Andrii Nakryiko' via syzkaller-bugs
> > <syzkaller-bugs@...glegroups.com> wrote:
> >>
> >> On 5/28/20 9:44 AM, syzbot wrote:
> >>> Hello,
> >>>
> >>> syzbot found the following crash on:
> >>>
> >>> HEAD commit:    dc0f3ed1 net: phy: at803x: add cable diagnostics support f..
> >>> git tree:       net-next
> >>> console output: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_log.txt-3Fx-3D17289cd2100000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=t1v5ZakZM9Aw_9u_I6FbFZ28U0GFs0e9dMMUOyiDxO4&e=
> >>> kernel config:  https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_.config-3Fx-3D7e1bc97341edbea6&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=yeXCTODuJF6ExmCJ-ppqMHsfvMCbCQ9zkmZi3W6NGHo&e=
> >>> dashboard link: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_bug-3Fextid-3D3610d489778b57cc8031&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=8fAJHh81yojiinnGJzTw6hN4w4A6XRZST4463CWL9Y8&e=
> >>> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> >>> syz repro:      https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_repro.syz-3Fx-3D15f237aa100000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=cPv-hQsGYs0CVz3I26BmauS0hQ8_YTWHeH5p-U5ElWY&e=
> >>> C reproducer:   https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_repro.c-3Fx-3D1553834a100000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=r6sGJDOgosZDE9sRxqFnVibDNJFt_6IteSWeqEQLbNE&e=
> >>>
> >>> The bug was bisected to:
> >>>
> >>> commit af6eea57437a830293eab56246b6025cc7d46ee7
> >>> Author: Andrii Nakryiko <andriin@...com>
> >>> Date:   Mon Mar 30 02:59:58 2020 +0000
> >>>
> >>>       bpf: Implement bpf_link-based cgroup BPF program attachment
> >>>
> >>> bisection log:  https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_bisect.txt-3Fx-3D1173cd7e100000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=rJIpYFSAMRfea3349dd7PhmLD_hriVwq8ZtTHcSagBA&e=
> >>> final crash:    https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_report.txt-3Fx-3D1373cd7e100000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=TWpx5JNdxKiKPABUScn8WB7u3fXueCp7BXwQHg4Unz0&e=
> >>> console output: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_log.txt-3Fx-3D1573cd7e100000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=-SMhn-dVZI4W51EZQ8Im0sdThgwt9M6fxUt3_bcYvk8&e=
> >>>
> >>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> >>> Reported-by: syzbot+3610d489778b57cc8031@...kaller.appspotmail.com
> >>> Fixes: af6eea57437a ("bpf: Implement bpf_link-based cgroup BPF program attachment")
> >>>
> >>> general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
> >>> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> >>> CPU: 0 PID: 7063 Comm: syz-executor654 Not tainted 5.7.0-rc6-syzkaller #0
> >>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> >>> RIP: 0010:inet_unhash+0x11f/0x770 net/ipv4/inet_hashtables.c:600
> >>
> >> No idea why it was bisected to bpf_link change. It seems completely
> >> struct sock-related. Seems like
> >
> > Hi Andrii,
> >
> > You can always find a detailed explanation of syzbot bisections under
> > the "bisection log" link.
>
> Right. Sorry, I didn't mean that bisect went wrong or anything like
> that. I just don't see how my change has anything to do with invalid
> socket state. As I just replied in another email, this particular repro
> is using bpf_link_create() for cgroup attachment, which was added in my
> patch. So running repro before my patch would always fail to attach BPF
> program, and thus won't be able to repro the issue (because the bug is
> somewhere in the interaction between BPF program attachment and socket
> itself). So it will always bisect to my patch :)

This happens sometimes. Sometimes bugs are bisected to the addition of
the debug check/tool. Which is... kinda working as intended. There is
only that much we can ask from the robot.

> >> struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
> >>
> >> ends up being NULL.
> >>
> >> Can some more networking-savvy people help with investigating this, please?
> >>
> >>> Code: 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e dd 04 00 00 48 8d 7d 08 44 8b 73 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 55 05 00 00 48 8d 7d 14 4c 8b 6d 08 48 b8 00 00
> >>> RSP: 0018:ffffc90001777d30 EFLAGS: 00010202
> >>> RAX: dffffc0000000000 RBX: ffff88809a6df940 RCX: ffffffff8697c242
> >>> RDX: 0000000000000001 RSI: ffffffff8697c251 RDI: 0000000000000008
> >>> RBP: 0000000000000000 R08: ffff88809f3ae1c0 R09: fffffbfff1514cc1
> >>> R10: ffffffff8a8a6607 R11: fffffbfff1514cc0 R12: ffff88809a6df9b0
> >>> R13: 0000000000000007 R14: 0000000000000000 R15: ffffffff873a4d00
> >>> FS:  0000000001d2b880(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> >>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>> CR2: 00000000006cd090 CR3: 000000009403a000 CR4: 00000000001406f0
> >>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>> Call Trace:
> >>>    sk_common_release+0xba/0x370 net/core/sock.c:3210
> >>>    inet_create net/ipv4/af_inet.c:390 [inline]
> >>>    inet_create+0x966/0xe00 net/ipv4/af_inet.c:248
> >>>    __sock_create+0x3cb/0x730 net/socket.c:1428
> >>>    sock_create net/socket.c:1479 [inline]
> >>>    __sys_socket+0xef/0x200 net/socket.c:1521
> >>>    __do_sys_socket net/socket.c:1530 [inline]
> >>>    __se_sys_socket net/socket.c:1528 [inline]
> >>>    __x64_sys_socket+0x6f/0xb0 net/socket.c:1528
> >>>    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
> >>>    entry_SYSCALL_64_after_hwframe+0x49/0xb3
> >>> RIP: 0033:0x441e29
> >>> Code: e8 fc b3 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 eb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> >>> RSP: 002b:00007ffdce184148 EFLAGS: 00000246 ORIG_RAX: 0000000000000029
> >>> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441e29
> >>> RDX: 0000000000000073 RSI: 0000000000000002 RDI: 0000000000000002
> >>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> >>> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> >>> R13: 0000000000402c30 R14: 0000000000000000 R15: 0000000000000000
> >>> Modules linked in:
> >>> ---[ end trace 23b6578228ce553e ]---
> >>> RIP: 0010:inet_unhash+0x11f/0x770 net/ipv4/inet_hashtables.c:600
> >>> Code: 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e dd 04 00 00 48 8d 7d 08 44 8b 73 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 55 05 00 00 48 8d 7d 14 4c 8b 6d 08 48 b8 00 00
> >>> RSP: 0018:ffffc90001777d30 EFLAGS: 00010202
> >>> RAX: dffffc0000000000 RBX: ffff88809a6df940 RCX: ffffffff8697c242
> >>> RDX: 0000000000000001 RSI: ffffffff8697c251 RDI: 0000000000000008
> >>> RBP: 0000000000000000 R08: ffff88809f3ae1c0 R09: fffffbfff1514cc1
> >>> R10: ffffffff8a8a6607 R11: fffffbfff1514cc0 R12: ffff88809a6df9b0
> >>> R13: 0000000000000007 R14: 0000000000000000 R15: ffffffff873a4d00
> >>> FS:  0000000001d2b880(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> >>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>> CR2: 00000000006cd090 CR3: 000000009403a000 CR4: 00000000001406f0
> >>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>>
> >>>
> >>> ---
> >>> This bug is generated by a bot. It may contain errors.
> >>> See https://urldefense.proofpoint.com/v2/url?u=https-3A__goo.gl_tpsmEJ&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=NELwknC4AyuWSJIHbwt_O_c0jfPc_6D9RuKHh_adQ_Y&e=  for more information about syzbot.
> >>> syzbot engineers can be reached at syzkaller@...glegroups.com.
> >>>
> >>> syzbot will keep track of this bug report. See:
> >>> https://urldefense.proofpoint.com/v2/url?u=https-3A__goo.gl_tpsmEJ-23status&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=YfV-e6A04EIqHwezxYop7CpJyhXD8DVzwTPUT0xckaM&e=  for how to communicate with syzbot.
> >>> For information about bisection process see: https://urldefense.proofpoint.com/v2/url?u=https-3A__goo.gl_tpsmEJ-23bisection&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=xOFzqI48uvECf4XFjlhNl4LBOT02lz1HlCL6MT1uMrI&e=
> >>> syzbot can test patches for this bug, for details see:
> >>> https://urldefense.proofpoint.com/v2/url?u=https-3A__goo.gl_tpsmEJ-23testing-2Dpatches&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=sMAtpavBBjBzFzT0V8c6FcH8cu2M9da3ZozO5Lc8do0&s=_cj6MOAz3yNlXgjMuyRu6ZOEjRvYWEvtTd7kE46wVfo&e=
> >>>
> >>
> >> --
> >> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> >> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@...glegroups.com.
> >> To view this discussion on the web visit https://urldefense.proofpoint.com/v2/url?u=https-3A__groups.google.com_d_msgid_syzkaller-2Dbugs_d65c8424-2De78c-2D63f9-2D3711-2D532494619dc6-2540fb.com&d=DwIFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=vxqvl81C2rT6GOGdPyz8iQ&m=b2VQiGg0nrxk96tqrmflMQ24DJk-MOxx4uyOs7wSUJ0&s=TYFus0Dh0-ZHiL510kJIyPOWCyX34UzLWR4QvS3r_iY&e= .
>

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