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=-15.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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=ham 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 E66AEC4320A for ; Mon, 30 Aug 2021 16:01:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C940060243 for ; Mon, 30 Aug 2021 16:01:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237893AbhH3QCA (ORCPT ); Mon, 30 Aug 2021 12:02:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42264 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237833AbhH3QB6 (ORCPT ); Mon, 30 Aug 2021 12:01:58 -0400 Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CDC3AC061575; Mon, 30 Aug 2021 09:01:04 -0700 (PDT) Received: by mail-pj1-x102b.google.com with SMTP id oa17so9823821pjb.1; Mon, 30 Aug 2021 09:01:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=fk7/r4wiBFQn4VdUenLsdi7Ji84YzGRrFf1wzmjaAi8=; b=aBseQnMae5mHee4uH+72B54i7StOjj5fUyCXFy0cxHf/IqhZT1m7bsdcjetZKS5KM+ W5mU1ZTbkSTRhFHfiKa4w2hRiNI6nkBPxwvnMTjHyzkv7G+pJPvtEqdaPFQ1hfmm04iQ iijWJZYd0vjVYsjy7Q2A9bk+8HV2OMp7Lxenuw4Kwxe1vG3CncQfyu48z082Q+vHaXLD jra6Fg5fgYB64cX84DV4GE5zfPwlm6q9iPPnwQMNzSwj5HchQ3KNvcC9c9vKqYp+D4Ez s+mfR96mtOZn2dMQUmxHY4Sfq4Xt4DcfrhVn7jQBmfaoZaMOBpGlrnOcVP1E7sJZ9chN P4jQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=fk7/r4wiBFQn4VdUenLsdi7Ji84YzGRrFf1wzmjaAi8=; b=SD0SDEMH9s7KmrqhfTmkYjqehhUMvxGFZtZbwxeYYkzXZqcf2nnIZs8eRkt7gq5xY+ IBdivhAAmfU1V05bu9o3K1Xwa3jte8gyoy0LBEgAM+pUTikNnXNUF6L318grGdJ2YJkF S25TJFa9OsUzP8wPEl3aRHtpbhwtQ6/1Et4dtELznNn+6cKkTGZJfTog5CspCcdsmdI7 EhNogOLEK5+tLG+Q7w1v7f4/uhyS+EsDjltvRAkLOXPjLUmrCrL3J9F51qQMgv43J4tl pLVbJjHZtDX50+moiXXUoU1ceyEQYeCjzE57FsqnhfSrbwuzJQ+p1Z8KOEgBkA3IxEO3 XMTg== X-Gm-Message-State: AOAM5327ocAeSBDg//gTjEMQu413u1gGvPM5fVxNeZwR4RLmBTz6NYcn 5sai221aMrDEeppK4j+ejEM= X-Google-Smtp-Source: ABdhPJzUZYGbQBQh0xlJfmCoBZK5gYWrJqYoI1syUuyy54FBztA/8jk16xOFSswZXTman0h7EswHng== X-Received: by 2002:a17:902:cec1:b0:138:e176:9676 with SMTP id d1-20020a170902cec100b00138e1769676mr320049plg.65.1630339264325; Mon, 30 Aug 2021 09:01:04 -0700 (PDT) Received: from [192.168.86.235] (c-73-241-150-58.hsd1.ca.comcast.net. [73.241.150.58]) by smtp.gmail.com with ESMTPSA id u21sm17896282pgk.57.2021.08.30.09.01.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Aug 2021 09:01:03 -0700 (PDT) Subject: Re: [PATCH v2] skb_expand_head() adjust skb->truesize incorrectly To: Vasily Averin , 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 References: <860513d5-fd02-832b-1c4c-ea2b17477d76@virtuozzo.com> From: Eric Dumazet Message-ID: <9f0c5e45-ad79-a9ea-dab1-aeb3bc3730ae@gmail.com> Date: Mon, 30 Aug 2021 09:01:01 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 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: linux-kernel@vger.kernel.org On 8/29/21 5:59 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 > > 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) { Unfortunately we can not always do this sk_wmem_alloc change here. Some skb have skb->sk set, but the 'reference on socket' is not through sk_wmem_alloc It seems you need a helper to make sure skb->destructor is one of the destructors that use skb->truesize and sk->sk_wmem_alloc For instance, skb_orphan_partial() could have been used. > + 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; > } >