[ 75/82] batman-adv: Only write requested number of byte to user buffer

[Ben Hutchings]

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sven Eckelmann <sven@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Signed-off-by: Marek Lindner <lindner_marek@xxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/batman-adv/icmp_socket.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- 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 fi
 
 	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)


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