Re: [PATCH v3] net: ipv6: fix skb_over_panic in __ip6_append_data

[Willem de Bruijn]

On Thu, Mar 10, 2022 at 6:26 PM Tadeusz Struk <tadeusz.struk@xxxxxxxxxx> wrote:
>
> Syzbot found a kernel bug in the ipv6 stack:
> LINK: https://syzkaller.appspot.com/bug?id=205d6f11d72329ab8d62a610c44c5e7e25415580
> The reproducer triggers it by sending a crafted message via sendmmsg()
> call, which triggers skb_over_panic, and crashes the kernel:
>
> skbuff: skb_over_panic: text:ffffffff84647fb4 len:65575 put:65575
> head:ffff888109ff0000 data:ffff888109ff0088 tail:0x100af end:0xfec0
> dev:<NULL>
>
> Update the check that prevents an invalid packet with MTU equall to the
> fregment header size to eat up all the space for payload.
>
> The reproducer can be found here:
> LINK: https://syzkaller.appspot.com/text?tag=ReproC&x=1648c83fb00000
>
> Cc: Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx>
> Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> Cc: Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>
> Cc: David Ahern <dsahern@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Cc: Martin KaFai Lau <kafai@xxxxxx>
> Cc: Song Liu <songliubraving@xxxxxx>
> Cc: Yonghong Song <yhs@xxxxxx>
> Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> Cc: KP Singh <kpsingh@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: bpf@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
>
> Reported-by: syzbot+e223cf47ec8ae183f2a0@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxxx>

Acked-by: Willem de Bruijn <willemb@xxxxxxxxxx>

small nit: "equal to the fragment" and all these Cc:s aren't really
needed in the commit message.

I don't think we'll find a commit for a Fixes tag. This goes ways back.