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Subject: Re: [PATCH net v10] skb_expand_head() adjust skb->truesize
 incorrectly
To:     Vasily Averin <vvs@virtuozzo.com>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        Jakub Kicinski <kuba@kernel.org>
Cc:     netdev <netdev@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>,
        Julian Wiedmann <jwi@linux.ibm.com>,
        Christoph Paasch <christoph.paasch@gmail.com>,
        linux-kernel@vger.kernel.org, kernel@openvz.org
References: <2721362c-462b-878f-9e09-9f6c4353c73d@gmail.com>
 <644330dd-477e-0462-83bf-9f514c41edd1@virtuozzo.com>
From:   Eric Dumazet <eric.dumazet@gmail.com>
Message-ID: <a55b298d-703f-d204-d425-a1d0704b2bb8@gmail.com>
Date:   Fri, 22 Oct 2021 12:32:35 -0700
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On 10/22/21 3:28 AM, Vasily Averin wrote:
> Christoph Paasch reports [1] about incorrect skb->truesize
> after skb_expand_head() call in ip6_xmit.
> This may happen because of two reasons:
> - skb_set_owner_w() for newly cloned skb is called too early,
> before pskb_expand_head() where truesize is adjusted for (!skb-sk) case.
> - pskb_expand_head() does not adjust truesize in (skb->sk) case.
> In this case sk->sk_wmem_alloc should be adjusted too.
> 
> [1] https://lkml.org/lkml/2021/8/20/1082
> 
> Fixes: f1260ff15a71 ("skbuff: introduce skb_expand_head()")
> Fixes: 2d85a1b31dde ("ipv6: ip6_finish_output2: set sk into newly allocated nskb")
> Reported-by: Christoph Paasch <christoph.paasch@gmail.com>
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
> ---
> v10: is_skb_wmem() was moved into separate header (it depends on net/tcp.h)
>      use it after pskb_expand_head() insted of strange sock_edemux check

SGTM, thanks !

Reviewed-by: Eric Dumazet <edumazet@google.com>