From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:42178 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965220AbbI2Ntl (ORCPT ); Tue, 29 Sep 2015 09:49:41 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Brenden Blanco , Herbert Xu , Konstantin Khlebnikov , "David S. Miller" Subject: [PATCH 3.10 41/56] net: Fix skb_set_peeked use-after-free bug Date: Tue, 29 Sep 2015 15:47:29 +0200 Message-Id: <20150929134702.196282456@linuxfoundation.org> In-Reply-To: <20150929134700.376714360@linuxfoundation.org> References: <20150929134700.376714360@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: stable-owner@vger.kernel.org List-ID: 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Herbert Xu [ Upstream commit a0a2a6602496a45ae838a96db8b8173794b5d398 ] 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: Greg Kroah-Hartman --- 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; } /** @@ -226,8 +226,9 @@ struct sk_buff *__skb_recv_datagram(stru 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);