From patchwork Mon Sep 6 18:01:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vasily Averin X-Patchwork-Id: 12477177 X-Patchwork-Delegate: kuba@kernel.org 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=-17.3 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,SPF_HELO_NONE,SPF_PASS,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 5F8FEC433FE for ; Mon, 6 Sep 2021 18:01:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3030060F45 for ; Mon, 6 Sep 2021 18:01:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244287AbhIFSC0 (ORCPT ); Mon, 6 Sep 2021 14:02:26 -0400 Received: from relay.sw.ru ([185.231.240.75]:56088 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230219AbhIFSCZ (ORCPT ); Mon, 6 Sep 2021 14:02:25 -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:Subject :From; bh=kcT8I0aFgFB3r1vKtYyJkIdbDQPWH1CpZGQzEdNUal0=; b=oC6cPW+kHrSjfB1C7+T LlB9GNlDjYjdRvJLx93UqTNIjSBBtpXdNEU4dYPavZFvLY+WrbyG1niiEZTmAVfUeviEewYCilZRi lq5VVn0zN8tUBFjp7bf0GwauB9/O/9BD0LRr/kXnNyco9ct1O0Y1/kPwELj9Dq0hFGQ5arhaUnY=; Received: from [10.93.0.56] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mNIvf-0013jq-Br; Mon, 06 Sep 2021 21:01:11 +0300 From: Vasily Averin Subject: [PATCH net v6] skb_expand_head() adjust skb->truesize incorrectly To: Christoph Paasch , Eric Dumazet , "David S. Miller" Cc: Hideaki YOSHIFUJI , David Ahern , Jakub Kicinski , netdev , linux-kernel@vger.kernel.org, kernel@openvz.org, Alexey Kuznetsov , Julian Wiedmann References: <63f90028-df26-d212-3bd2-65168736ce06@virtuozzo.com> Message-ID: Date: Mon, 6 Sep 2021 21:01:10 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <63f90028-df26-d212-3bd2-65168736ce06@virtuozzo.com> Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org 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 Signed-off-by: Vasily Averin --- v6: fixed delta, improved comments 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 | 60 ++++++++++++++++++++++++++++++++++++++++++++++-------- net/core/sock.c | 8 ++++++++ 3 files changed, 60 insertions(+), 9 deletions(-) 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..e2a2aa31 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1804,28 +1804,70 @@ 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. */ 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 = skb_end_offset(skb) - osize; + /* skb_set_owner_w() calls current skb destructor. + * It can reduce sk_wmem_alloc to 0 and release sk, + * To prevnt this, we increase sk_wmem_alloc in advance. + * Some destructors might release the last sk_refcnt, + * so it won't be possible to call sock_hold for !fullsock + * We take an extra sk_refcnt to prevent this. + * In any case we 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