batman-adv: Only write requested number of byte to user buffer

commit b5a1eeef04cc7859f34dec9b72ea1b28e4aba07c upstream.

Don't write more than the requested number of bytes of an batman-adv icmp
packet to the userspace buffer. Otherwise unrelated userspace memory might get
overridden by the kernel.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/batman-adv/icmp_socket.c b/net/batman-adv/icmp_socket.c
index a9d85853d2bca6e634f1ebe51e39e4c76b4ed203..0c82ce3b80f54c236c7ccc2a40c3b0b0671c17e9 100644 (file)
--- a/net/batman-adv/icmp_socket.c
+++ b/net/batman-adv/icmp_socket.c
@@ -136,10 +136,9 @@ static ssize_t bat_socket_read(struct file *file, char __user *buf,
 
        spin_unlock_bh(&socket_client->lock);
 
-       error = copy_to_user(buf, &socket_packet->icmp_packet,
-                            socket_packet->icmp_len);
+       packet_len = min(count, socket_packet->icmp_len);
+       error = copy_to_user(buf, &socket_packet->icmp_packet, packet_len);
 
-       packet_len = socket_packet->icmp_len;
        kfree(socket_packet);
 
        if (error)