netdev - Re: [PATCH net-next] rxrpc: uninitialized variable in rxrpc_send_ack

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Date:   Thu, 17 Nov 2022 09:44:24 +0000
From:   David Howells <dhowells@...hat.com>
To:     Dan Carpenter <error27@...il.com>
Cc:     dhowells@...hat.com, Marc Dionne <marc.dionne@...istor.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-afs@...ts.infradead.org,
        netdev@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net-next] rxrpc: uninitialized variable in rxrpc_send_ack_packet()

Dan Carpenter <error27@...il.com> wrote:

> The "pkt" was supposed to have been deleted in a previous patch.  It
> leads to an uninitialized variable bug.

Weird.  I don't get a compiler warning and the kernel doesn't crash, despite
transmitting millions of acks.

If I disassemble the built code, I see:

   0xffffffff81b09e89 <+723>:   xor    %edi,%edi
   0xffffffff81b09e8b <+725>:   call   0xffffffff811c0bc1 <kfree>

I'm not sure why it's sticking 0 in EDI, though.

David