From patchwork Fri Oct 22 10:28:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vasily Averin X-Patchwork-Id: 12577511 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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29850C433EF for ; Fri, 22 Oct 2021 10:29:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 03E7260FBF for ; Fri, 22 Oct 2021 10:29:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232539AbhJVKbW (ORCPT ); Fri, 22 Oct 2021 06:31:22 -0400 Received: from relay.sw.ru ([185.231.240.75]:57254 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232483AbhJVKbU (ORCPT ); Fri, 22 Oct 2021 06:31:20 -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=XQ6Ahg85i45HJD/1pzC326y13kc7dgKywmzoKnkSAn8=; b=ZYlerleCmMyBLkC/HsF T+OpLAUDsBywovDRHJd6fHPdsNHfrGJk1ZqvJO5kTyAzqSrLl8kPC0cog00oK2lnccYVeUth+Sx2w mwxXREGc1fWsjwuyiQIpD5YTQQJ5h1L8lxPLnLS721GMO1R3qkjOzo2SkGb2Owv7sWbRiKJXo8Y=; Received: from [172.29.1.17] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mdrnH-006pEx-4a; Fri, 22 Oct 2021 13:28:59 +0300 From: Vasily Averin Subject: [PATCH net v10] skb_expand_head() adjust skb->truesize incorrectly To: Eric Dumazet , Jakub Kicinski Cc: netdev , "David S. Miller" , "David S. Miller" , Hideaki YOSHIFUJI , David Ahern , Julian Wiedmann , Christoph Paasch , linux-kernel@vger.kernel.org, kernel@openvz.org References: <2721362c-462b-878f-9e09-9f6c4353c73d@gmail.com> Message-ID: <644330dd-477e-0462-83bf-9f514c41edd1@virtuozzo.com> Date: Fri, 22 Oct 2021 13:28:37 +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: <2721362c-462b-878f-9e09-9f6c4353c73d@gmail.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 Reviewed-by: Eric Dumazet --- v10: is_skb_wmem() was moved into separate header (it depends on net/tcp.h) use it after pskb_expand_head() insted of strange sock_edemux check v9: restored sock_edemux check v8: clone non-wmem skb v7 (from kuba@): shift more magic into helpers, follow Eric's advice and don't inherit non-wmem skbs for now 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. net/core/skbuff.c | 36 +++++++++++++++++++++++------------- net/core/sock_destructor.h | 12 ++++++++++++ 2 files changed, 35 insertions(+), 13 deletions(-) create mode 100644 net/core/sock_destructor.h diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 2170bea2c7de..fe9358437380 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -80,6 +80,7 @@ #include #include "datagram.h" +#include "sock_destructor.h" struct kmem_cache *skbuff_head_cache __ro_after_init; static struct kmem_cache *skbuff_fclone_cache __ro_after_init; @@ -1804,30 +1805,39 @@ EXPORT_SYMBOL(skb_realloc_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 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. */ + if (skb_shared(skb) || !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 { - kfree_skb(skb); - } + if (unlikely(!nskb)) + goto fail; + + if (sk) + skb_set_owner_w(nskb, sk); + consume_skb(skb); skb = nskb; } - if (skb && - pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) { - kfree_skb(skb); - skb = NULL; + if (pskb_expand_head(skb, delta, 0, GFP_ATOMIC)) + goto fail; + + if (sk && is_skb_wmem(skb)) { + delta = skb_end_offset(skb) - osize; + refcount_add(delta, &sk->sk_wmem_alloc); + skb->truesize += delta; } return skb; + +fail: + kfree_skb(skb); + return NULL; } EXPORT_SYMBOL(skb_expand_head); diff --git a/net/core/sock_destructor.h b/net/core/sock_destructor.h new file mode 100644 index 000000000000..2f396e6bfba5 --- /dev/null +++ b/net/core/sock_destructor.h @@ -0,0 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#ifndef _NET_CORE_SOCK_DESTRUCTOR_H +#define _NET_CORE_SOCK_DESTRUCTOR_H +#include + +static inline 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); +} +#endif