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,URIBL_BLOCKED autolearn=ham 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 1831CC433ED for ; Fri, 9 Apr 2021 00:26:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8C4260FE8 for ; Fri, 9 Apr 2021 00:26:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232958AbhDIA0j (ORCPT ); Thu, 8 Apr 2021 20:26:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41654 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232951AbhDIA0j (ORCPT ); Thu, 8 Apr 2021 20:26:39 -0400 Received: from mail-io1-xd2b.google.com (mail-io1-xd2b.google.com [IPv6:2607:f8b0:4864:20::d2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB973C061760; Thu, 8 Apr 2021 17:26:27 -0700 (PDT) Received: by mail-io1-xd2b.google.com with SMTP id r193so4142059ior.9; Thu, 08 Apr 2021 17:26:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:content-transfer-encoding; bh=qAptFUU90Znoha/E9NINSsAXDHdY41JcMDe7P0BQ2Yg=; b=lqAGPuzRmQzOkMzEJ9f0AoMW+aNm0bys8BXHQIwaHKHGSBML0IDUTzNKKH3ch1XqPN VkmHxyqWhT2OmqMAtrliPhTJ6RJcf/6sOgYJAPjLBUEQyviZpLUpWz4Z+e0ckkD2vcVa 5W0omj+G0zkx55JP5i1w7lhfz/R1whTl8FBuFc4nC1Ro9gVNSmxuxo3BNVpjBzUDdWS4 A9jR/+pguoo3iuT9N1vfW6GmBcF7VBOB4o4bdZzYAz6XdkV/YPxrcF4jDfQitgBUy7R1 Pm8f+g/fhldAB12N62U06LPaFa3RxMq+Xhjgn6FFXepOdE/8jXjXP1b5PUttC9zE+HCI hD4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version:content-transfer-encoding; bh=qAptFUU90Znoha/E9NINSsAXDHdY41JcMDe7P0BQ2Yg=; b=cb6winHOUCxqUO0Y7qRKBapePl4LQiGVW+PYHxr8oSaZEYK2aR8RWdwWQkYkYiM2qQ 6HwqJDXmMw2Mfg+nDfKpP0Q4MLFc54dwKa2GYfVoYmljOPl8Jk+X1dwpJXmr08EY0w/+ tGSv0wwp9GE3T/mbT1SGK1mHmH2a3vFxA4gECVR//4m2dNzgIdorp2c8rkykTKwChRf1 7v+ltOzLhcDUd6ghzIK21B9dBLB1Qs0aRIj3nHOU/6kFbA9wd2cMVf6LMgCl+nn9bYqW FpG2wNUaK+/b05tnCsJK7sX9XzoF4ux3P9u0BSom6KL2NLrQb+8T8N7O7gBIDaenNyDv DKhg== X-Gm-Message-State: AOAM530jk4m5PROt1Yf3yiT9YV8wpx0WEgBwzjCxxcDzVZHculn/TeaI Uy/GXtKGQi7v012ksMFjygA= X-Google-Smtp-Source: ABdhPJwNBeyYBBhR5PYARBaEDWRkA3HCI5UnZZMdpyf1XJ8WKww02UwfsAbdyg7KmbNmVeWgO9ichw== X-Received: by 2002:a6b:8b0e:: with SMTP id n14mr9145619iod.199.1617927987114; Thu, 08 Apr 2021 17:26:27 -0700 (PDT) Received: from localhost ([172.242.244.146]) by smtp.gmail.com with ESMTPSA id k11sm455905ilv.73.2021.04.08.17.26.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Apr 2021 17:26:26 -0700 (PDT) Date: Thu, 08 Apr 2021 17:26:19 -0700 From: John Fastabend To: Cong Wang , netdev@vger.kernel.org Cc: bpf@vger.kernel.org, Cong Wang , syzbot+7b6548ae483d6f4c64ae@syzkaller.appspotmail.com, John Fastabend , Daniel Borkmann , Jakub Sitnicki , Lorenz Bauer Message-ID: <606f9f2b26b1a_c8b9208a4@john-XPS-13-9370.notmuch> In-Reply-To: <20210408030556.45134-1-xiyou.wangcong@gmail.com> References: <20210408030556.45134-1-xiyou.wangcong@gmail.com> Subject: RE: [Patch bpf-next] sock_map: fix a potential use-after-free in sock_map_close() Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Cong Wang wrote: > From: Cong Wang > > The last refcnt of the psock can be gone right after > sock_map_remove_links(), so sk_psock_stop() could trigger a UAF. > The reason why I placed sk_psock_stop() there is to avoid RCU read > critical section, and more importantly, some callee of > sock_map_remove_links() is supposed to be called with RCU read lock, > we can not simply get rid of RCU read lock here. Therefore, the only > choice we have is to grab an additional refcnt with sk_psock_get() > and put it back after sk_psock_stop(). > > Reported-by: syzbot+7b6548ae483d6f4c64ae@syzkaller.appspotmail.com > Fixes: 799aa7f98d53 ("skmsg: Avoid lock_sock() in sk_psock_backlog()") > Cc: John Fastabend > Cc: Daniel Borkmann > Cc: Jakub Sitnicki > Cc: Lorenz Bauer > Signed-off-by: Cong Wang > --- > net/core/sock_map.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/core/sock_map.c b/net/core/sock_map.c > index f473c51cbc4b..6f1b82b8ad49 100644 > --- a/net/core/sock_map.c > +++ b/net/core/sock_map.c > @@ -1521,7 +1521,7 @@ void sock_map_close(struct sock *sk, long timeout) > > lock_sock(sk); > rcu_read_lock(); It looks like we can drop the rcu_read_lock()/unlock() section then if we take a reference on the psock? Before it was there to ensure we didn't lose the psock from some other context, but with a reference held this can not happen. > - psock = sk_psock(sk); > + psock = sk_psock_get(sk); > if (unlikely(!psock)) { > rcu_read_unlock(); > release_sock(sk); > @@ -1532,6 +1532,7 @@ void sock_map_close(struct sock *sk, long timeout) > sock_map_remove_links(sk, psock); > rcu_read_unlock(); > sk_psock_stop(psock, true); > + sk_psock_put(sk, psock); > release_sock(sk); > saved_close(sk, timeout); > } > -- > 2.25.1 >