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=-12.8 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 AE369C47096 for ; Thu, 3 Jun 2021 22:32:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8A3CB613FF for ; Thu, 3 Jun 2021 22:32:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231154AbhFCWeN (ORCPT ); Thu, 3 Jun 2021 18:34:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37170 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230158AbhFCWeM (ORCPT ); Thu, 3 Jun 2021 18:34:12 -0400 Received: from mail-pf1-x434.google.com (mail-pf1-x434.google.com [IPv6:2607:f8b0:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50BA1C061756; Thu, 3 Jun 2021 15:32:15 -0700 (PDT) Received: by mail-pf1-x434.google.com with SMTP id y15so6001066pfl.4; Thu, 03 Jun 2021 15:32:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=VUfhHlJEUkLIR0EIxU6jXP1bVKyAro32mftomoJHVSQ=; b=dUPVKRvL4ucDTigXFTP29OZzBupoPFAqKnumC/amO0ZZob6v9CW5aE4LOAqGxSf8wr ANTBNXdTwzx5qLAEqsY0zwPXZIx6ivvToN4ROae9vwyVyWlzoasf45Ox7dB46fDqOYZK iPcfopWe8E3qRgMt5BMYXfcgNfns7gNV7kHNZHtew3gwZ2E4NRXEGnNgJQpSwH2iJMCh jaoruUrycy6WDokpMWZC7egJxhYWTzLCjfEThi6hvCdTvxgj0gNN0ZtqrKUrmqIltoux Fk7/XOj4c/3WhFXPst67wIAQXDZxqAKKPpCQdJOlc8SvfBINGYo1sFqzkr2heuecq6pY /Kbg== 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=VUfhHlJEUkLIR0EIxU6jXP1bVKyAro32mftomoJHVSQ=; b=MfXYNwKUK3NeWuUpuOoeYbEgXHtTp1FSIcN6iCXbTz1RT7er4vx65zH/o7kTLWYUi/ OdCETT17SAgCkK+cTHxkY2jOfBS6rLABAqLM70DM55Gs4JrsvUl+35QviDJ3WpqpLeCd 6TXtn4yw1ElUpwBWYcnZu7DkkEyxxTZEQjtBNUpEL6F+Ca2Wh8nx11s+uefQg3rTTuLI yGbwewWbxjtgQlZcHdA6lWblVnsZUtZpbDPXX4+JqXlK4km6GE8KjoWfIvvOCMU025VV J7ARfzpQMMnAzSQVghrrZsd8xp2TWfKrssyqNDV8654VCvB4awOVISbqcyk9HtApl4ix qatg== X-Gm-Message-State: AOAM530UhQfw7ovtvn926adnMLaIu7sYfR6GP4cFDhxF7Bd6fCDayD/C gtVLcZmLCcKsNfb0rQawzXSFybbAJmdmWC8KISDO1cNi1H3vPQ== X-Google-Smtp-Source: ABdhPJzOTpRU3MtYwgO5eoq3M8jObwOxfDBiaRLRIFQsvqlRRCSPIIi4n0fauN6h3W6Gzr4IxnzGjlhxqWzJRB8nn/Y= X-Received: by 2002:a63:571d:: with SMTP id l29mr1628701pgb.179.1622759534685; Thu, 03 Jun 2021 15:32:14 -0700 (PDT) MIME-Version: 1.0 References: <20210602192640.13597-1-paskripkin@gmail.com> In-Reply-To: <20210602192640.13597-1-paskripkin@gmail.com> From: Cong Wang Date: Thu, 3 Jun 2021 15:32:03 -0700 Message-ID: Subject: Re: [PATCH] net: kcm: fix memory leak in kcm_sendmsg To: Pavel Skripkin Cc: David Miller , Jakub Kicinski , Tom Herbert , Linux Kernel Network Developers , LKML , syzbot+b039f5699bd82e1fb011@syzkaller.appspotmail.com, stable Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Jun 2, 2021 at 12:29 PM Pavel Skripkin wrote: > > Syzbot reported memory leak in kcm_sendmsg()[1]. > The problem was in non-freed frag_list in case of error. > > In the while loop: > > if (head == skb) > skb_shinfo(head)->frag_list = tskb; > else > skb->next = tskb; > > frag_list filled with skbs, but nothing was freeing them. What do you mean by "nothing was freeing them"? I am sure kfree_skb() will free those in frag_list: 654 static void skb_release_data(struct sk_buff *skb) 655 { 656 struct skb_shared_info *shinfo = skb_shinfo(skb); 657 int i; ... 669 if (shinfo->frag_list) 670 kfree_skb_list(shinfo->frag_list); > > backtrace: > [<0000000094c02615>] __alloc_skb+0x5e/0x250 net/core/skbuff.c:198 > [<00000000e5386cbd>] alloc_skb include/linux/skbuff.h:1083 [inline] > [<00000000e5386cbd>] kcm_sendmsg+0x3b6/0xa50 net/kcm/kcmsock.c:967 [1] > [<00000000f1613a8a>] sock_sendmsg_nosec net/socket.c:652 [inline] > [<00000000f1613a8a>] sock_sendmsg+0x4c/0x60 net/socket.c:672 > > Reported-and-tested-by: syzbot+b039f5699bd82e1fb011@syzkaller.appspotmail.com > Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") > Cc: stable@vger.kernel.org > Signed-off-by: Pavel Skripkin > --- > net/kcm/kcmsock.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c > index 6201965bd822..1c572c8daced 100644 > --- a/net/kcm/kcmsock.c > +++ b/net/kcm/kcmsock.c > @@ -1066,6 +1066,11 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) > goto partial_message; > } > > + if (skb_has_frag_list(head)) { > + kfree_skb_list(skb_shinfo(head)->frag_list); > + skb_shinfo(head)->frag_list = NULL; > + } > + > if (head != kcm->seq_skb) > kfree_skb(head); This exact kfree_skb() should free those in frag_list. If the above if condition does not meet for some reason, then fix that condition? Thanks.