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net: ipv4: fix for a race condition in raw_sendmsg

PATCH In review [email protected] 3 participants 3 messages Dec 10, 2017 – Dec 11, 2017

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#0 lore raw

PATCH 1/1 net: ipv4: fix for a race condition in raw_sendmsg

From: Mohamed Ghannam <[email protected]>

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

Signed-off-by Mohamed Ghannam <[email protected]>
---
 net/ipv4/raw.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)
net/ipv4/raw.c +10 -5
index 33b70bfd1122..125c1eab3eaa 100644
@@ -513,11 +513,16 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	int err;
 	struct ip_options_data opt_copy;
 	struct raw_frag_vec rfv;
+	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.
 	 */

@@ -593,7 +598,7 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		/* 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)

@@ -615,12 +620,12 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 	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, sk->sk_uid);
 
-	if (!inet->hdrincl) {
+	if (!hdrincl) {
 		rfv.msg = msg;
 		rfv.hlen = 0;
 

@@ -645,7 +650,7 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		goto do_confirm;
 back_from_confirm:
 
-	if (inet->hdrincl)
+	if (hdrincl)
 		err = raw_send_hdrinc(sk, &fl4, msg, len,
 				      &rt, msg->msg_flags, &ipc.sockc);
Signature · 1 line
2.14.1
Reviewed-by on v1 1/1
#1 lore raw
Quoted 9 lines · On Sun, 2017-12-10 at 03:50 +0000, [email protected] wrote:

From: Mohamed Ghannam <[email protected]>

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

Signed-off-by Mohamed Ghannam <[email protected]>

---
 net/ipv4/raw.c | 15 ++++++++++-----

 1 file changed, 10 insertions(+), 5 deletions(-)

Thanks a lot for fixing this very serious bug.

Reviewed-by Eric Dumazet <[email protected]>

Please David add :

Fixes c008ba5bdc9f ("ipv4: Avoid reading user iov twice after raw_probe_proto_opt")

Thanks !