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Date: Tue, 6 May 2025 19:20:30 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Matt Johnston <matt@codeconstruct.com.au>
Cc: Jeremy Kerr <jk@codeconstruct.com.au>, "David S. Miller"
 <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Paolo Abeni
 <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
 netdev@vger.kernel.org,
 syzbot+e76d52dadc089b9d197f@syzkaller.appspotmail.com,
 syzbot+1065a199625a388fce60@syzkaller.appspotmail.com
Subject: Re: [PATCH net] net: mctp: Don't access ifa_index when missing
Message-ID: <20250506192030.7228fcc9@kernel.org>
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On Wed, 07 May 2025 10:13:19 +0800 Matt Johnston wrote:
> > I see your point. And existing user space may expect filtering
> > even if !cb->strict_check but family is set to AF_MCTP?  
> 
> Yes, given mctp_dump_addrinfo() has always applied a filter, mctp-specific
> programs likely expect that behaviour.

Okay, so would this make all known user space happy?

	if (!msg short) {
		ifindex = ifm->ifa_index
	} else {
		if (cb->strict_check)
			return error
	}

I suspect busybox doesn't set strict check, otherwise it'd trip up in IP