Re: [PATCH mptcp-net] mptcp: fix uninit-value in mptcp_established_options

[Matthieu Baerts <matttbe@kernel.org>]

Hi Paolo,

On 29/05/2026 19:13, Paolo Abeni wrote:
> syzbot reported the following uninit splat:
> 
> =====================================================

(...)

> =====================================================
> 
> The output path currently omit initializing the mptcp extension `use_map`
> flag in a few corner cases.
> Address the issue always zeroing all the extensions flags before
> eventually initializing the individual bits. To that extent, introduce
> and use a struct_group to avoid multiple bitwise operations.
> 
> Reported-by: syzbot+ff020673c5e3d94d9478@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=ff020673c5e3d94d9478
> Fixes: 6d0060f600ad ("mptcp: Write MPTCP DSS headers to outgoing data packets")

Small detail: I hope that's OK to use this one instead:

  cfcceb7a39fc ("tcp: shrink per-packet memset in __tcp_transmit_skb()")

Before this commit, the whole "opts" was set to 0. So no need to
backport this "too far".

Also, because of the issue reported by the 0day bot, I will wait a few
more days before sending this patch upstream.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.