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=-12.7 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,SPF_HELO_NONE,SPF_PASS 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 A2F2BC432BE for ; Thu, 2 Sep 2021 15:53:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 769BE610A2 for ; Thu, 2 Sep 2021 15:53:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234411AbhIBPyu (ORCPT ); Thu, 2 Sep 2021 11:54:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234405AbhIBPyo (ORCPT ); Thu, 2 Sep 2021 11:54:44 -0400 Received: from mail-ej1-x62a.google.com (mail-ej1-x62a.google.com [IPv6:2a00:1450:4864:20::62a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 977A6C061575; Thu, 2 Sep 2021 08:53:45 -0700 (PDT) Received: by mail-ej1-x62a.google.com with SMTP id bt14so5499895ejb.3; Thu, 02 Sep 2021 08:53:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=wjiK60A2GTYsSOEiStHsCNnHBinVI+innS9X3/HkY6A=; b=NraQocpmXy8PTjNMammi7bWOsB3mOCLjofzO5D6yE4j0UEfSXtV9t8eK3MCC06Z4FF gu1h0LxZ9Ta9uNidVz3HwhUTe+zaAtnNZMVo59McGG3eseewVYXxWZg7zJWLpsaSGBaL Xq9kneXtXiLsEBes3e/0t0bFpFCO7Ur7VPjMKtJ8IHUxly3C4NNSTaFM1v3OGwr5qCJk xhmNTZYXmBq2RfffXni52BPeZH0OEYPgBIDXx+QpNFwzSUZ8MIFtTM378YtAzD6wAFJb yP7umI262k0GE9RK/sl5Fg9VLyf1XW3gzkqZ7yTAJYJ3Sk4jik1JF6wDso+gnrJrspod Wrhg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=wjiK60A2GTYsSOEiStHsCNnHBinVI+innS9X3/HkY6A=; b=H2JkYK4BP90eNo8HH+uq4exqxjJtdudPO/FI+cmTfbzb3jHCdqYlqCiyu3hI7s5bQp CqIqXghbjIz8oAosbLBlO9joSuT85w1BYgqMzccpO9R1+8UVlE9GxzqBIBJjQXcJamU9 16AagyjnsvMihWFbxZUFB6Vph8TAI5mKHAK/XDvjeUde6iCMoTjX5UdR6kOE3UhubWN3 fCk0VDoulXbCt5kghk3ocFWhOHNsUBoc3fKQUb4g13Y0PBitp7vvNaXmO3v5cEn1oyH6 3nM7sU6E2yk3M0/WoltJHPYNsHAJXLiOOs8+JFj4mxO1qjaEnOpgXLAxYr1zA9fjabp/ 0b1g== X-Gm-Message-State: AOAM533r/24T663ZK9h4K4NcxhIkqJrJdjHQHDlH90GloR1gq3GIzRtt ZoGQVZaBaQD1aaW7VsQ7yi9M0bEheTkr7qpXMrg= X-Google-Smtp-Source: ABdhPJxqKevZRGoNwDtwRU3RcR/gmbyBQ32TVMKZV/NAsJVJwajeYZRoGCJOBrzDnSqzRQwqkvwJvm+zKEt+fjMVNE8= X-Received: by 2002:a17:906:774f:: with SMTP id o15mr4594148ejn.200.1630598024011; Thu, 02 Sep 2021 08:53:44 -0700 (PDT) MIME-Version: 1.0 References: <27f87dd8-f6e4-b2b0-2b3a-9378fddf147f@virtuozzo.com> <053307fc-cc3d-68f5-1994-fe447428b1f2@virtuozzo.com> In-Reply-To: <053307fc-cc3d-68f5-1994-fe447428b1f2@virtuozzo.com> From: Christoph Paasch Date: Thu, 2 Sep 2021 08:53:32 -0700 Message-ID: Subject: Re: [PATCH net-next v5] skb_expand_head() adjust skb->truesize incorrectly To: Vasily Averin Cc: Eric Dumazet , "David S. Miller" , Hideaki YOSHIFUJI , David Ahern , Jakub Kicinski , netdev , LKML , kernel@openvz.org, Alexey Kuznetsov , Julian Wiedmann Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 2, 2021 at 4:12 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()") > Reported-by: Christoph Paasch > Signed-off-by: Vasily Averin > --- > v5: fixed else condition, thanks to Eric > reworked update of expanded skb, > added corresponding comments > v4: decided to use is_skb_wmem() after pskb_expand_head() call > fixed 'return (EXPRESSION);' in os_skb_wmem according to Eric Dumazet > v3: removed __pskb_expand_head(), > added is_skb_wmem() helper for skb with wmem-compatible destructors > there are 2 ways to use it: > - before pskb_expand_head(), to create skb clones > - after successfull pskb_expand_head() to change owner on extended skb. > 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. > --- > include/net/sock.h | 1 + > net/core/skbuff.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++-------- > net/core/sock.c | 8 +++++++ > 3 files changed, 63 insertions(+), 9 deletions(-) Still the same issues around refcount as I reported in my other email. Did you try running the syzkaller reproducer on your setup? Christoph > > diff --git a/include/net/sock.h b/include/net/sock.h > index 95b2577..173d58c 100644 > --- a/include/net/sock.h > +++ b/include/net/sock.h > @@ -1695,6 +1695,7 @@ struct sk_buff *sock_wmalloc(struct sock *sk, unsigned long size, int force, > gfp_t priority); > void __sock_wfree(struct sk_buff *skb); > void sock_wfree(struct sk_buff *skb); > +bool is_skb_wmem(const struct sk_buff *skb); > struct sk_buff *sock_omalloc(struct sock *sk, unsigned long size, > gfp_t priority); > void skb_orphan_partial(struct sk_buff *skb); > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index f931176..29bb92e7 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -1804,28 +1804,73 @@ 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); > + int osize = skb_end_offset(skb); > + struct sk_buff *oskb = NULL; > + struct sock *sk = skb->sk; > > if (WARN_ONCE(delta <= 0, > "%s is expecting an increase in the headroom", __func__)) > return skb; > > - /* pskb_expand_head() might crash, if skb is shared */ > + delta = SKB_DATA_ALIGN(delta); > + /* pskb_expand_head() might crash, if skb is shared. > + * Also we should clone skb if its destructor does > + * not adjust skb->truesize and sk->sk_wmem_alloc > + */ > 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)) { > kfree_skb(skb); > - skb = NULL; > + kfree_skb(oskb); > + return NULL; > + } > + if (oskb) { > + if (sk) > + skb_set_owner_w(skb, sk); > + consume_skb(oskb); > + } else if (sk && skb->destructor != sock_edemux) { > + bool ref, set_owner; > + > + ref = false; set_owner = false; > + delta = osize - skb_end_offset(skb); > + /* skb_set_owner_w() calls current skb destructor. > + * It can decrease sk_wmem_alloc to 0 and release sk, > + * To prevnt it we increase sk_wmem_alloc earlier. > + * Another kind of destructors can release last sk_refcnt, > + * so it will be impossible to call sock_hold for !fullsock > + * Take extra sk_refcnt to prevent it. > + * Otherwise just increase truesize of expanded skb. > + */ > + refcount_add(delta, &sk->sk_wmem_alloc); > + if (!is_skb_wmem(skb)) { > + set_owner = true; > + if (!sk_fullsock(sk) && IS_ENABLED(CONFIG_INET)) { > + /* skb_set_owner_w can set sock_edemux */ > + ref = refcount_inc_not_zero(&sk->sk_refcnt); > + if (!ref) { > + set_owner = false; > + WARN_ON(refcount_sub_and_test(delta, &sk->sk_wmem_alloc)); > + } > + } > + } > + if (set_owner) > + skb_set_owner_w(skb, sk); > +#ifdef CONFIG_INET > + if (skb->destructor == sock_edemux) { > + WARN_ON(refcount_sub_and_test(delta, &sk->sk_wmem_alloc)); > + if (ref) > + WARN_ON(refcount_dec_and_test(&sk->sk_refcnt)); > + } > +#endif > + skb->truesize += delta; > } > return skb; > } > diff --git a/net/core/sock.c b/net/core/sock.c > index 950f1e7..6cbda43 100644 > --- a/net/core/sock.c > +++ b/net/core/sock.c > @@ -2227,6 +2227,14 @@ void skb_set_owner_w(struct sk_buff *skb, struct sock *sk) > } > EXPORT_SYMBOL(skb_set_owner_w); > > +bool is_skb_wmem(const struct sk_buff *skb) > +{ > + return skb->destructor == sock_wfree || > + skb->destructor == __sock_wfree || > + (IS_ENABLED(CONFIG_INET) && skb->destructor == tcp_wfree); > +} > +EXPORT_SYMBOL(is_skb_wmem); > + > static bool can_skb_orphan_partial(const struct sk_buff *skb) > { > #ifdef CONFIG_TLS_DEVICE > -- > 1.8.3.1 >