From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6539C4320A for ; Mon, 30 Aug 2021 05:53:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95B5D60FBF for ; Mon, 30 Aug 2021 05:53:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232521AbhH3Fxy (ORCPT ); Mon, 30 Aug 2021 01:53:54 -0400 Received: from relay.sw.ru ([185.231.240.75]:48032 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231741AbhH3Fxw (ORCPT ); Mon, 30 Aug 2021 01:53:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:From: Subject; bh=CZGtUolhje7Vsk3gbqjS0thLrINH1hLljA/H/12io0E=; b=H9wsO24Iz+sDH3ehq 0dj5woeHzyyWljn/zso5+TQ9UVplmy/Bi+okE788RCXG9cvxSog+zYK2vS92Fb9vkpv9Mf/VP9LEs ZI2yN8jm66AhnqgOgLtoTJFmLuG+D70K9EeZcKdtqEE/tvuYlxh3DkDUNQa7V5saqrnidkr0p0ZTM =; Received: from [10.93.0.56] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mKaDx-000AK5-RU; Mon, 30 Aug 2021 08:52:49 +0300 Subject: Re: [PATCH net-next v2] skb_expand_head() adjust skb->truesize incorrectly From: Vasily Averin To: Christoph Paasch , Eric Dumazet , "David S. Miller" Cc: Hideaki YOSHIFUJI , David Ahern , Jakub Kicinski , netdev , linux-kernel@vger.kernel.org, kernel@openvz.org, Julian Wiedmann , Alexey Kuznetsov References: <860513d5-fd02-832b-1c4c-ea2b17477d76@virtuozzo.com> Message-ID: <835071d6-88e8-902e-4997-042bf4b84b6f@virtuozzo.com> Date: Mon, 30 Aug 2021 08:52:49 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <860513d5-fd02-832b-1c4c-ea2b17477d76@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 1) I forgot to specify that the patch is intended fro net-next git 2) I forgot to ad Alexey Kuznetsov in cc. I resend the patch to him in a separate letter and received his consent. 3) I forgot to set Fixed mark Fixes: f1260ff15a71 ("skbuff: introduce skb_expand_head()") Thank you, Vasily Averin On 8/29/21 3:59 PM, 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 > > Reported-by: Christoph Paasch > Signed-off-by: Vasily Averin > --- > v2: based on patch version from Eric Dumazet, > added __pskb_expand_head() function, which can be forced > to adjust skb->truesize and sk->sk_wmem_alloc. > --- > net/core/skbuff.c | 43 +++++++++++++++++++++++++++++-------------- > 1 file changed, 29 insertions(+), 14 deletions(-) > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index f931176..4691023 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -1681,10 +1681,10 @@ struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom, > * reloaded after call to this function. > */ > > -int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, > - gfp_t gfp_mask) > +static int __pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, > + gfp_t gfp_mask, bool update_truesize) > { > - int i, osize = skb_end_offset(skb); > + int delta, i, osize = skb_end_offset(skb); > int size = osize + nhead + ntail; > long off; > u8 *data; > @@ -1756,9 +1756,13 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, > * For the moment, we really care of rx path, or > * when skb is orphaned (not attached to a socket). > */ > - if (!skb->sk || skb->destructor == sock_edemux) > - skb->truesize += size - osize; > - > + delta = size - osize; > + if (!skb->sk || skb->destructor == sock_edemux) { > + skb->truesize += delta; > + } else if (update_truesize) { > + refcount_add(delta, &skb->sk->sk_wmem_alloc); > + skb->truesize += delta; > + } > return 0; > > nofrags: > @@ -1766,6 +1770,12 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, > nodata: > return -ENOMEM; > } > + > +int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, > + gfp_t gfp_mask) > +{ > + return __pskb_expand_head(skb, nhead, ntail, gfp_mask, false); > +} > EXPORT_SYMBOL(pskb_expand_head); > > /* Make private copy of skb with writable head and some headroom */ > @@ -1804,28 +1814,33 @@ struct sk_buff *skb_realloc_headroom(struct sk_buff *skb, unsigned int headroom) > struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom) > { > int delta = headroom - skb_headroom(skb); > + struct sk_buff *oskb = NULL; > > if (WARN_ONCE(delta <= 0, > "%s is expecting an increase in the headroom", __func__)) > return skb; > > + delta = SKB_DATA_ALIGN(delta); > /* pskb_expand_head() might crash, if skb is shared */ > if (skb_shared(skb)) { > struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC); > > - if (likely(nskb)) { > - if (skb->sk) > - skb_set_owner_w(nskb, skb->sk); > - consume_skb(skb); > - } else { > + if (unlikely(!nskb)) { > kfree_skb(skb); > + return NULL; > } > + oskb = skb; > skb = nskb; > } > - if (skb && > - pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) { > + if (__pskb_expand_head(skb, delta, 0, GFP_ATOMIC, true)) { > kfree_skb(skb); > - skb = NULL; > + kfree_skb(oskb); > + return NULL; > + } > + if (oskb) { > + if (oskb->sk) > + skb_set_owner_w(skb, oskb->sk); > + consume_skb(oskb); > } > return skb; > } >