net: heap overflow in __audit_sockaddr()

[ Upstream commit 1661bf36 ]

We need to cap ->msg_namelen or it leads to a buffer overflow when we
to the memcpy() in __audit_sockaddr().  It requires CAP_AUDIT_CONTROL to
exploit this bug.

The call tree is:
___sys_recvmsg()
  move_addr_to_user()
    audit_sockaddr()
      __audit_sockaddr()
Reported-by: Jri Aedla <juri.aedla@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[wt: 2.6.32: msg_sys is a struct, not a pointer]
Signed-off-by: Willy Tarreau <w@1wt.eu>

net/compat.c

@@ -69,6 +69,8 @@ int get_compat_msghdr(struct msghdr *kmsg, struct compat_msghdr __user *umsg)
 	    __get_user(kmsg->msg_controllen, &umsg->msg_controllen) ||
 	    __get_user(kmsg->msg_flags, &umsg->msg_flags))
 		return -EFAULT;
+	if (kmsg->msg_namelen > sizeof(struct sockaddr_storage))
+		return -EINVAL;
 	kmsg->msg_name = compat_ptr(tmp1);
 	kmsg->msg_iov = compat_ptr(tmp2);
 	kmsg->msg_control = compat_ptr(tmp3);

net/socket.c

@@ -1863,6 +1863,16 @@ SYSCALL_DEFINE2(shutdown, int, fd, int, how)
 #define COMPAT_NAMELEN(msg)	COMPAT_MSG(msg, msg_namelen)
 #define COMPAT_FLAGS(msg)	COMPAT_MSG(msg, msg_flags)
 
+static int copy_msghdr_from_user(struct msghdr *kmsg,
+                                 struct msghdr __user *umsg)
+{
+	if (copy_from_user(kmsg, umsg, sizeof(struct msghdr)))
+		return -EFAULT;
+	if (kmsg->msg_namelen > sizeof(struct sockaddr_storage))
+		return -EINVAL;
+	return 0;
+}
+
 /*
  *	BSD sendmsg interface
  */
@@ -1887,8 +1897,11 @@ SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned, flags)
 		if (get_compat_msghdr(&msg_sys, msg_compat))
 			return -EFAULT;
 	}
-	else if (copy_from_user(&msg_sys, msg, sizeof(struct msghdr)))
-		return -EFAULT;
+	else {
+		err = copy_msghdr_from_user(&msg_sys, msg);
+		if (err)
+			return err;
+	}
 
 	sock = sockfd_lookup_light(fd, &err, &fput_needed);
 	if (!sock)
@@ -1997,8 +2010,11 @@ SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
 		if (get_compat_msghdr(&msg_sys, msg_compat))
 			return -EFAULT;
 	}
-	else if (copy_from_user(&msg_sys, msg, sizeof(struct msghdr)))
-		return -EFAULT;
+	else {
+		err = copy_msghdr_from_user(&msg_sys, msg);
+		if (err)
+			return err;
+	}
 
 	sock = sockfd_lookup_light(fd, &err, &fput_needed);
 	if (!sock)