From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933501AbbIDNfD (ORCPT ); Fri, 4 Sep 2015 09:35:03 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:50145 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932934AbbIDNJq (ORCPT ); Fri, 4 Sep 2015 09:09:46 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Herbert Xu , "David S. Miller" , Luis Henriques Subject: [PATCH 3.16.y-ckt 070/130] net: Fix skb_set_peeked use-after-free bug Date: Fri, 4 Sep 2015 14:07:38 +0100 Message-Id: <1441372118-5933-71-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1441372118-5933-1-git-send-email-luis.henriques@canonical.com> References: <1441372118-5933-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt17 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Herbert Xu 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: Luis Henriques --- 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 2b2ed1ae5b63..3c69a464595e 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -130,12 +130,12 @@ 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)) @@ -143,7 +143,7 @@ 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; @@ -156,7 +156,7 @@ static int skb_set_peeked(struct sk_buff *skb) done: skb->peeked = 1; - return 0; + return skb; } /** @@ -228,8 +228,9 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, continue; } - 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);