[PATCH] ping: prevent NULL pointer dereference on write to msg_name

[PATCH] ping: prevent NULL pointer dereference on write to msg_name

[Hannes Frederic Sowa]

A plain read() on a socket does set msg->msg_name to NULL. So check for
NULL pointer first.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
---

Addendum to "[v4] inet: prevent leakage of uninitialized memory to user in
recv syscalls".

 net/ipv4/ping.c | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index aacefa0..91bfe04 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -870,11 +870,13 @@ int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	if (family == AF_INET) {
 		struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
 
-		sin->sin_family = AF_INET;
-		sin->sin_port = 0 /* skb->h.uh->source */;
-		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
-		memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
-		*addr_len = sizeof(*sin);
+		if (sin) {
+			sin->sin_family = AF_INET;
+			sin->sin_port = 0 /* skb->h.uh->source */;
+			sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
+			memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
+			*addr_len = sizeof(*sin);
+		}
 
 		if (isk->cmsg_flags)
 			ip_cmsg_recv(msg, skb);
@@ -886,16 +888,18 @@ int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 		struct sockaddr_in6 *sin6 =
 			(struct sockaddr_in6 *)msg->msg_name;
 
-		sin6->sin6_family = AF_INET6;
-		sin6->sin6_port = 0;
-		sin6->sin6_addr = ip6->saddr;
-		sin6->sin6_flowinfo = 0;
-		if (np->sndflow)
-			sin6->sin6_flowinfo = ip6_flowinfo(ip6);
-
-		sin6->sin6_scope_id = ipv6_iface_scope_id(&sin6->sin6_addr,
-							  IP6CB(skb)->iif);
-		*addr_len = sizeof(*sin6);
+		if (sin6) {
+			sin6->sin6_family = AF_INET6;
+			sin6->sin6_port = 0;
+			sin6->sin6_addr = ip6->saddr;
+			sin6->sin6_flowinfo = 0;
+			if (np->sndflow)
+				sin6->sin6_flowinfo = ip6_flowinfo(ip6);
+			sin6->sin6_scope_id =
+				ipv6_iface_scope_id(&sin6->sin6_addr,
+						    IP6CB(skb)->iif);
+			*addr_len = sizeof(*sin6);
+		}
 
 		if (inet6_sk(sk)->rxopt.all)
 			pingv6_ops.ip6_datagram_recv_ctl(sk, msg, skb);
-- 
1.8.3.1

Re: [PATCH] ping: prevent NULL pointer dereference on write to msg_name

[David Miller]

From: Hannes Frederic Sowa <hannes@stressinduktion.org>
Date: Mon, 18 Nov 2013 07:07:45 +0100

> A plain read() on a socket does set msg->msg_name to NULL. So check for
> NULL pointer first.
> 
> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> ---
> 
> Addendum to "[v4] inet: prevent leakage of uninitialized memory to user in
> recv syscalls".

Applied and queued up for -stable, thanks Hannes.

Looks like ipv6 got this case right.

Re: [PATCH] ping: prevent NULL pointer dereference on write to msg_name

[Hannes Frederic Sowa]

On Mon, Nov 18, 2013 at 04:02:38PM -0500, David Miller wrote:
> From: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Date: Mon, 18 Nov 2013 07:07:45 +0100
> 
> > A plain read() on a socket does set msg->msg_name to NULL. So check for
> > NULL pointer first.
> > 
> > Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> > ---
> > 
> > Addendum to "[v4] inet: prevent leakage of uninitialized memory to user in
> > recv syscalls".
> 
> Applied and queued up for -stable, thanks Hannes.
> 
> Looks like ipv6 got this case right.

No, IPv6 reuses the IPv4 recvmsg handler. The patch fixes that as well.

Thanks,

  Hannes