From patchwork Wed Apr 14 10:48:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Abeni X-Patchwork-Id: 12202323 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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 6BAF0C433ED for ; Wed, 14 Apr 2021 10:49:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4DB4C61249 for ; Wed, 14 Apr 2021 10:49:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234020AbhDNKtm (ORCPT ); Wed, 14 Apr 2021 06:49:42 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:59439 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233897AbhDNKt2 (ORCPT ); Wed, 14 Apr 2021 06:49:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618397342; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=We9uznYlK5dDZxYFXapdGy47V4QK+f7aFI5+V/isz3E=; b=hDMN/KvQbyuca5T6NawzgVPVyXH99HmqJGX86v8Sf23UEsgqDxhYfYQumiy2voZPUv+dq5 GoeW8KKLolfEVbLTpRbmR7t7BUhZzhLHZdGId0m0txz13+X6QQlrCu9f+9QkofL86xhcQz zbT9jXBh+zX/9xi8D2JaujZqYnfWDhE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-306-FmX7bh8WNxWSGVe29FSozw-1; Wed, 14 Apr 2021 06:49:01 -0400 X-MC-Unique: FmX7bh8WNxWSGVe29FSozw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1E265186833B; Wed, 14 Apr 2021 10:49:00 +0000 (UTC) Received: from gerbillo.redhat.com (ovpn-113-255.ams2.redhat.com [10.36.113.255]) by smtp.corp.redhat.com (Postfix) with ESMTP id B063B610A8; Wed, 14 Apr 2021 10:48:58 +0000 (UTC) From: Paolo Abeni To: netdev@vger.kernel.org Cc: Yunsheng Lin , Dongseok Yi , Willem de Bruijn Subject: [PATCH net-next] skbuff: revert "skbuff: remove some unnecessary operation in skb_segment_list()" Date: Wed, 14 Apr 2021 12:48:48 +0200 Message-Id: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org the commit 1ddc3229ad3c ("skbuff: remove some unnecessary operation in skb_segment_list()") introduces an issue very similar to the one already fixed by commit 53475c5dd856 ("net: fix use-after-free when UDP GRO with shared fraglist"). If the GSO skb goes though skb_clone() and pskb_expand_head() before entering skb_segment_list(), the latter will unshare the frag_list skbs and will release the old list. With the reverted commit in place, when skb_segment_list() completes, skb->next points to the just released list, and later on the kernel will hit UaF. Note that since commit e0e3070a9bc9 ("udp: properly complete L4 GRO over UDP tunnel packet") the critical scenario can be reproduced also receiving UDP over vxlan traffic with: NIC (NETIF_F_GRO_FRAGLIST enabled) -> vxlan -> UDP sink Attaching a packet socket to the NIC will cause skb_clone() and the tunnel decapsulation will call pskb_expand_head(). Fixes: 1ddc3229ad3c ("skbuff: remove some unnecessary operation in skb_segment_list()") Signed-off-by: Paolo Abeni --- net/core/skbuff.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 3ad9e8425ab2..14010c0eec48 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3773,13 +3773,13 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb, unsigned int tnl_hlen = skb_tnl_header_len(skb); unsigned int delta_truesize = 0; unsigned int delta_len = 0; + struct sk_buff *tail = NULL; struct sk_buff *nskb, *tmp; int err; skb_push(skb, -skb_network_offset(skb) + offset); skb_shinfo(skb)->frag_list = NULL; - skb->next = list_skb; do { nskb = list_skb; @@ -3797,8 +3797,17 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb, } } - if (unlikely(err)) + if (!tail) + skb->next = nskb; + else + tail->next = nskb; + + if (unlikely(err)) { + nskb->next = list_skb; goto err_linearize; + } + + tail = nskb; delta_len += nskb->len; delta_truesize += nskb->truesize; @@ -3825,7 +3834,7 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb, skb_gso_reset(skb); - skb->prev = nskb; + skb->prev = tail; if (skb_needs_linearize(skb, features) && __skb_linearize(skb))