netdev - Re: [PATCH] rxrpc: Initialize sockaddr

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Message-ID: <883286.1731942012@warthog.procyon.org.uk>
Date: Mon, 18 Nov 2024 15:00:12 +0000
From: David Howells <dhowells@...hat.com>
To: Matt Jan <zoo868e@...il.com>
Cc: dhowells@...hat.com,
    syzbot+14c04e62ca58315571d1@...kaller.appspotmail.com,
    davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
    linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org,
    marc.dionne@...istor.com, netdev@...r.kernel.org, pabeni@...hat.com,
    syzkaller-bugs@...glegroups.com, skhan@...uxfoundation.org
Subject: Re: [PATCH] rxrpc: Initialize sockaddr_rxrpc directly

Matt Jan <zoo868e@...il.com> wrote:

> In rxrpc_lookup_peer_local_rcu(), removed the redundant memset call
> that zeros out the sockaddr_rxrpc structure before setting its fields.
> Instead, initialize the sockaddr_rxrpc structure directly in
> rxrpc_input_error().
> 
> This change simplifies the code and ensures that the sockaddr_rxrpc
> structure is properly zero-initialized.

How does that actually fix the issue?

All the patch does is move the initialisation of srx from
rxrpc_lookup_peer_local_rcu() into its only caller - and nothing samples the
contents of srx between.

Looking at the bug report, the history of the uninitialised location goes back
further, to a network address generated/assembled in the ipv6 stack or from
the transmission side of the rxrpc stack, possibly call->peer->srx.transport.

David