From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753541AbbK2WIT (ORCPT ); Sun, 29 Nov 2015 17:08:19 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:56737 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752912AbbK2WII (ORCPT ); Sun, 29 Nov 2015 17:08:08 -0500 Message-Id: <20151129214703.386380700@1wt.eu> User-Agent: quilt/0.63-1 Date: Sun, 29 Nov 2015 22:47:14 +0100 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Brenden Blanco , Herbert Xu , Konstantin Khlebnikov , "David S. Miller" , Ben Hutchings , Willy Tarreau Subject: [PATCH 2.6.32 12/38] [PATCH 12/38] net: Fix skb_set_peeked use-after-free bug MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 In-Reply-To: <8acf8256ccc72771a80b7851061027bc@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ commit a0a2a6602496a45ae838a96db8b8173794b5d398 upstream. The commit 738ac1ebb96d02e0d23bc320302a6ea94c612dec ("net: Clone skb before setting peeked flag") introduced a use-after-free bug in skb_recv_datagram. This is because skb_set_peeked may create a new skb and free the existing one. As it stands the caller will continue to use the old freed skb. This patch fixes it by making skb_set_peeked return the new skb (or the old one if unchanged). Fixes: 738ac1ebb96d ("net: Clone skb before setting peeked flag") Reported-by: Brenden Blanco Signed-off-by: Herbert Xu Tested-by: Brenden Blanco Reviewed-by: Konstantin Khlebnikov Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings (cherry picked from commit e553622ccb6b6e06079f980f55cf04128db3420c) Signed-off-by: Willy Tarreau --- net/core/datagram.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/net/core/datagram.c b/net/core/datagram.c index cbb3100..c855336 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -127,12 +127,12 @@ out_noerr: goto out; } -static int skb_set_peeked(struct sk_buff *skb) +static struct sk_buff *skb_set_peeked(struct sk_buff *skb) { struct sk_buff *nskb; if (skb->peeked) - return 0; + return skb; /* We have to unshare an skb before modifying it. */ if (!skb_shared(skb)) @@ -140,7 +140,7 @@ static int skb_set_peeked(struct sk_buff *skb) nskb = skb_clone(skb, GFP_ATOMIC); if (!nskb) - return -ENOMEM; + return ERR_PTR(-ENOMEM); skb->prev->next = nskb; skb->next->prev = nskb; @@ -153,7 +153,7 @@ static int skb_set_peeked(struct sk_buff *skb) done: skb->peeked = 1; - return 0; + return skb; } /** @@ -214,8 +214,9 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags, *peeked = skb->peeked; if (flags & MSG_PEEK) { - error = skb_set_peeked(skb); - if (error) + skb = skb_set_peeked(skb); + error = PTR_ERR(skb); + if (IS_ERR(skb)) goto unlock_err; atomic_inc(&skb->users); -- 1.7.12.2.21.g234cd45.dirty