[PATCH 3.18 27/32] net: ipv4: fix for a race condition in raw_sendmsg - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Mohamed Ghannam <simo.ghannam@gmail.com>,
	Eric Dumazet <edumazet@google.com>,
	"David S. Miller" <davem@davemloft.net>
Subject: [PATCH 3.18 27/32] net: ipv4: fix for a race condition in raw_sendmsg
Date: Mon,  1 Jan 2018 15:22:34 +0100	[thread overview]
Message-ID: <20180101140018.584848542@linuxfoundation.org> (raw)
In-Reply-To: <20180101140012.582300879@linuxfoundation.org>

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mohamed Ghannam <simo.ghannam@gmail.com>


[ Upstream commit 8f659a03a0ba9289b9aeb9b4470e6fb263d6f483 ]

inet->hdrincl is racy, and could lead to uninitialized stack pointer
usage, so its value should be read only once.

Fixes: c008ba5bdc9f ("ipv4: Avoid reading user iov twice after raw_probe_proto_opt")
Signed-off-by: Mohamed Ghannam <simo.ghannam@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/raw.c |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -483,11 +483,16 @@ static int raw_sendmsg(struct kiocb *ioc
 	u8  tos;
 	int err;
 	struct ip_options_data opt_copy;
+	int hdrincl;
 
 	err = -EMSGSIZE;
 	if (len > 0xFFFF)
 		goto out;
 
+	/* hdrincl should be READ_ONCE(inet->hdrincl)
+	 * but READ_ONCE() doesn't work with bit fields
+	 */
+	hdrincl = inet->hdrincl;
 	/*
 	 *	Check the flags.
 	 */
@@ -560,7 +565,7 @@ static int raw_sendmsg(struct kiocb *ioc
 		/* Linux does not mangle headers on raw sockets,
 		 * so that IP options + IP_HDRINCL is non-sense.
 		 */
-		if (inet->hdrincl)
+		if (hdrincl)
 			goto done;
 		if (ipc.opt->opt.srr) {
 			if (!daddr)
@@ -582,12 +587,12 @@ static int raw_sendmsg(struct kiocb *ioc
 
 	flowi4_init_output(&fl4, ipc.oif, sk->sk_mark, tos,
 			   RT_SCOPE_UNIVERSE,
-			   inet->hdrincl ? IPPROTO_RAW : sk->sk_protocol,
+			   hdrincl ? IPPROTO_RAW : sk->sk_protocol,
 			   inet_sk_flowi_flags(sk) |
-			    (inet->hdrincl ? FLOWI_FLAG_KNOWN_NH : 0),
+			    (hdrincl ? FLOWI_FLAG_KNOWN_NH : 0),
 			   daddr, saddr, 0, 0);
 
-	if (!inet->hdrincl) {
+	if (!hdrincl) {
 		err = raw_probe_proto_opt(&fl4, msg);
 		if (err)
 			goto done;
@@ -609,7 +614,7 @@ static int raw_sendmsg(struct kiocb *ioc
 		goto do_confirm;
 back_from_confirm:
 
-	if (inet->hdrincl)
+	if (hdrincl)
 		err = raw_send_hdrinc(sk, &fl4, msg->msg_iov, len,
 				      &rt, msg->msg_flags);
 
