From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030987Ab2HGWmq (ORCPT ); Tue, 7 Aug 2012 18:42:46 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:47761 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030970Ab2HGWmm (ORCPT ); Tue, 7 Aug 2012 18:42:42 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg KH , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Lin Ming , Paul Moore , "David S. Miller" Subject: [ 085/109] cipso: dont follow a NULL pointer when setsockopt() is called Date: Tue, 7 Aug 2012 15:35:44 -0700 Message-Id: <20120807222050.547018094@linuxfoundation.org> X-Mailer: git-send-email 1.7.10.1.362.g242cab3 In-Reply-To: <20120807222043.089735600@linuxfoundation.org> References: <20120807222043.089735600@linuxfoundation.org> User-Agent: quilt/0.60-20.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Greg KH 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paul Moore [ Upstream commit 89d7ae34cdda4195809a5a987f697a517a2a3177 ] As reported by Alan Cox, and verified by Lin Ming, when a user attempts to add a CIPSO option to a socket using the CIPSO_V4_TAG_LOCAL tag the kernel dies a terrible death when it attempts to follow a NULL pointer (the skb argument to cipso_v4_validate() is NULL when called via the setsockopt() syscall). This patch fixes this by first checking to ensure that the skb is non-NULL before using it to find the incoming network interface. In the unlikely case where the skb is NULL and the user attempts to add a CIPSO option with the _TAG_LOCAL tag we return an error as this is not something we want to allow. A simple reproducer, kindly supplied by Lin Ming, although you must have the CIPSO DOI #3 configure on the system first or you will be caught early in cipso_v4_validate(): #include #include #include #include #include struct local_tag { char type; char length; char info[4]; }; struct cipso { char type; char length; char doi[4]; struct local_tag local; }; int main(int argc, char **argv) { int sockfd; struct cipso cipso = { .type = IPOPT_CIPSO, .length = sizeof(struct cipso), .local = { .type = 128, .length = sizeof(struct local_tag), }, }; memset(cipso.doi, 0, 4); cipso.doi[3] = 3; sockfd = socket(AF_INET, SOCK_DGRAM, 0); #define SOL_IP 0 setsockopt(sockfd, SOL_IP, IP_OPTIONS, &cipso, sizeof(struct cipso)); return 0; } CC: Lin Ming Reported-by: Alan Cox Signed-off-by: Paul Moore Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/cipso_ipv4.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/net/ipv4/cipso_ipv4.c +++ b/net/ipv4/cipso_ipv4.c @@ -1725,8 +1725,10 @@ int cipso_v4_validate(const struct sk_bu case CIPSO_V4_TAG_LOCAL: /* This is a non-standard tag that we only allow for * local connections, so if the incoming interface is - * not the loopback device drop the packet. */ - if (!(skb->dev->flags & IFF_LOOPBACK)) { + * not the loopback device drop the packet. Further, + * there is no legitimate reason for setting this from + * userspace so reject it if skb is NULL. */ + if (skb == NULL || !(skb->dev->flags & IFF_LOOPBACK)) { err_offset = opt_iter; goto validate_return_locked; }