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[23.128.96.18]) by mx.google.com with ESMTP id 2si17638183iob.47.2021.08.31.07.36.24; Tue, 31 Aug 2021 07:36:36 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=relay header.b=brfqHMCW; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=virtuozzo.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238284AbhHaOf0 (ORCPT + 99 others); Tue, 31 Aug 2021 10:35:26 -0400 Received: from relay.sw.ru ([185.231.240.75]:45648 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234845AbhHaOfZ (ORCPT ); Tue, 31 Aug 2021 10:35:25 -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=3y3a0G9JOqOLl1XXFRKNLkkT/vIWt1LlgMq53mTUC6U=; b=brfqHMCWyeI/RD7xYkr xGsXMqL2DGVgLzdz2FU3T7mFop2/m3hjmnbijJkNizAt+K588YQWRpZzm4hqGw+HIFyeIZJOB0v9o ly199lwEOKmgyg/PlQsJmexvrAOX+uynpqzvbnapaLfDBFolsv9EgFQJQU5QoT881/uvRrbjLWY=; Received: from [10.93.0.56] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mL4qB-000N5z-W4; Tue, 31 Aug 2021 17:34:19 +0300 From: Vasily Averin Subject: [PATCH net-next v3 RFC] 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, Julian Wiedmann , Alexey Kuznetsov References: <8fd56805-2ac8-dcbe-1337-b20f91f759d6@gmail.com> Message-ID: Date: Tue, 31 Aug 2021 17:34:19 +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: <8fd56805-2ac8-dcbe-1337-b20f91f759d6@gmail.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 RFC because it have an extra changes: new is_skb_wmem() helper can be called - either before pskb_expand_head(), to create skb clones for skb with destructors that does not change sk->sk_wmem_alloc - or after pskb_expand_head(), to change owner in skb_set_owner_w() In current patch I've added both these ways, we need to keep one of them. --- 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 --- 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 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 | 39 ++++++++++++++++++++++++++++----------- net/core/sock.c | 8 ++++++++ 3 files changed, 37 insertions(+), 11 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..3ce33f2 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1804,30 +1804,47 @@ 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 */ - if (skb_shared(skb)) { + 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) || + (sk && (!sk_fullsock(sk) || !is_skb_wmem(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; } - return skb; + if (oskb) { + if (sk) + skb_set_owner_w(skb, sk); + consume_skb(oskb); + } else if (sk) { + delta = osize - skb_end_offset(skb); + if (!is_skb_wmem(skb)) + skb_set_owner_w(skb, sk); + skb->truesize += delta; + if (sk_fullsock(sk)) + refcount_add(delta, &sk->sk_wmem_alloc); + } return skb; } EXPORT_SYMBOL(skb_expand_head); diff --git a/net/core/sock.c b/net/core/sock.c index 950f1e7..0315dcb 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