netdev - Re: [PATCH net] net: always initialize pagedlen

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Message-Id: <20181124.174336.2013396951281875471.davem@davemloft.net>
Date:   Sat, 24 Nov 2018 17:43:36 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     willemdebruijn.kernel@...il.com
Cc:     netdev@...r.kernel.org, willemb@...gle.com
Subject: Re: [PATCH net] net: always initialize pagedlen

From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Date: Sat, 24 Nov 2018 14:21:16 -0500

> From: Willem de Bruijn <willemb@...gle.com>
> 
> In ip packet generation, pagedlen is initialized for each skb at the
> start of the loop in __ip(6)_append_data, before label alloc_new_skb.
> 
> Depending on compiler options, code can be generated that jumps to
> this label, triggering use of an an uninitialized variable.
> 
> In practice, at -O2, the generated code moves the initialization below
> the label. But the code should not rely on that for correctness.
> 
> Fixes: 15e36f5b8e98 ("udp: paged allocation with gso")
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> 
> ---
> 
> Noticed when rebasing udp zerocopy. I considered merging as part of
> that patchset, but this seemed like it should go to net, even if it
> does not trigger in practice.
> 
> Merged net with this patch onto net-next with udp zerocopy to verify
> that there is no merge conflict.

Ok, applied, but not queued for -stable.

Let me know if I should -stable this.