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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Martin KaFai Lau <kafai@fb.com>
Cc:     andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
        daniel@iogearbox.net, davem@davemloft.net, hawk@kernel.org,
        john.fastabend@gmail.com, kpsingh@kernel.org, kuba@kernel.org,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        songliubraving@fb.com, syzkaller-bugs@googlegroups.com, yhs@fb.com,
        syzbot <syzbot+0e91362d99386dc5de99@syzkaller.appspotmail.com>
Subject: Re: [syzbot] BUG: missing reserved tailroom
In-Reply-To: <20220310210626.25o2mll3jmp62swy@kafai-mbp.dhcp.thefacebook.com>
References: <00000000000019c51e05d9e18158@google.com>
 <20220310210626.25o2mll3jmp62swy@kafai-mbp.dhcp.thefacebook.com>
Date:   Thu, 10 Mar 2022 22:57:52 +0100
Message-ID: <87ee39xyfz.fsf@toke.dk>
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Martin KaFai Lau <kafai@fb.com> writes:

> On Thu, Mar 10, 2022 at 10:37:20AM -0800, syzbot wrote:
>> Hello,
>>=20
>> syzbot found the following issue on:
>>=20
>> HEAD commit:    de55c9a1967c Merge branch 'Add support for transmitting =
pa..
>> git tree:       bpf-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=3D14ce88ad7000=
00
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=3D2fa13781bcea=
50fc
>> dashboard link: https://syzkaller.appspot.com/bug?extid=3D0e91362d99386d=
c5de99
>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binut=
ils for Debian) 2.35.2
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=3D11f3634570=
0000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=3D14c8ca657000=
00
>>=20
>> The issue was bisected to:
>>=20
>> commit b530e9e1063ed2b817eae7eec6ed2daa8be11608
>> Author: Toke H=C3=B8iland-J=C3=B8rgensen <toke@redhat.com>
>> Date:   Wed Mar 9 10:53:42 2022 +0000
>>=20
>>     bpf: Add "live packet" mode for XDP in BPF_PROG_RUN
>>=20
>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=3D17696e557=
00000
>> final oops:     https://syzkaller.appspot.com/x/report.txt?x=3D14e96e557=
00000
>> console output: https://syzkaller.appspot.com/x/log.txt?x=3D10e96e557000=
00
>>=20
>> IMPORTANT: if you fix the issue, please add the following tag to the com=
mit:
>> Reported-by: syzbot+0e91362d99386dc5de99@syzkaller.appspotmail.com
>> Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in BPF_PROG_RU=
N")
>>=20
>> ------------[ cut here ]------------
>> XDP_WARN: xdp_update_frame_from_buff(line:274): Driver BUG: missing rese=
rved tailroom
>> WARNING: CPU: 0 PID: 3590 at net/core/xdp.c:599 xdp_warn+0x28/0x30 net/c=
ore/xdp.c:599
> Toke, please take a look.

Right, I see the problem; will send a fix!

-Toke