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Date: Tue, 2 Feb 2021 18:59:40 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Marco Elver <elver@...gle.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
kasan-dev <kasan-dev@...glegroups.com>,
David Miller <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Jonathan Lemon <jonathan.lemon@...il.com>,
Willem de Bruijn <willemb@...gle.com>,
linmiaohe <linmiaohe@...wei.com>,
Guillaume Nault <gnault@...hat.com>,
Dongseok Yi <dseok.yi@...sung.com>,
Yadu Kishore <kyk.segfault@...il.com>,
Al Viro <viro@...iv.linux.org.uk>,
netdev <netdev@...r.kernel.org>,
Alexander Potapenko <glider@...gle.com>,
syzbot <syzbot+7b99aafdcc2eedea6178@...kaller.appspotmail.com>
Subject: Re: [PATCH net-next] net: fix up truesize of cloned skb in skb_prepare_for_shift()
On Mon, Feb 1, 2021 at 5:04 PM Marco Elver <elver@...gle.com> wrote:
>
> Avoid the assumption that ksize(kmalloc(S)) == ksize(kmalloc(S)): when
> cloning an skb, save and restore truesize after pskb_expand_head(). This
> can occur if the allocator decides to service an allocation of the same
> size differently (e.g. use a different size class, or pass the
> allocation on to KFENCE).
>
> Because truesize is used for bookkeeping (such as sk_wmem_queued), a
> modified truesize of a cloned skb may result in corrupt bookkeeping and
> relevant warnings (such as in sk_stream_kill_queues()).
>
> Link: https://lkml.kernel.org/r/X9JR/J6dMMOy1obu@elver.google.com
> Reported-by: syzbot+7b99aafdcc2eedea6178@...kaller.appspotmail.com
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Marco Elver <elver@...gle.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
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