From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758980AbbJIAUf (ORCPT ); Thu, 8 Oct 2015 20:20:35 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:35471 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758983AbbJIARd (ORCPT ); Thu, 8 Oct 2015 20:17:33 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David S. Miller" , "Herbert Xu" , "Brenden Blanco" , "Konstantin Khlebnikov" Date: Fri, 09 Oct 2015 01:12:27 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 017/107] net: Fix skb_set_peeked use-after-free bug In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.247 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.72-rc1 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: Ben Hutchings --- net/core/datagram.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -128,12 +128,12 @@ 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)) @@ -141,7 +141,7 @@ static int skb_set_peeked(struct sk_buff nskb = skb_clone(skb, GFP_ATOMIC); if (!nskb) - return -ENOMEM; + return ERR_PTR(-ENOMEM); skb->prev->next = nskb; skb->next->prev = nskb; @@ -154,7 +154,7 @@ static int skb_set_peeked(struct sk_buff done: skb->peeked = 1; - return 0; + return skb; } /** @@ -216,8 +216,9 @@ struct sk_buff *__skb_recv_datagram(stru *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);