Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030786Ab2HQDdj (ORCPT ); Thu, 16 Aug 2012 23:33:39 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:46776 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030646Ab2HQD07 (ORCPT ); Thu, 16 Aug 2012 23:26:59 -0400 Message-Id: <20120817030244.580052425@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Fri, 17 Aug 2012 04:02:48 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Paul Moore , Lin Ming , "David S. Miller" Subject: [ 05/37] cipso: dont follow a NULL pointer when setsockopt() is called In-Reply-To: <20120817030243.807605523@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 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 Content-Length: 3019 Lines: 99 3.2-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: Ben Hutchings --- net/ipv4/cipso_ipv4.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c index 86f3b88..afaa735 100644 --- a/net/ipv4/cipso_ipv4.c +++ b/net/ipv4/cipso_ipv4.c @@ -1725,8 +1725,10 @@ int cipso_v4_validate(const struct sk_buff *skb, unsigned char **option) 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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/