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

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>

1 files changed, 2 insertions, 3 deletions

diff --git a/net/batman-adv/icmp_socket.c b/net/batman-adv/icmp_socket.c
index 3b04fff3ede3..d9c1e7bb7fbf 100644
--- 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)