[B.A.T.M.A.N.] [PATCHv3 1/2] batman-adv: Only write requested number of byte to user buffer

Sven Eckelmann sven at narfation.org
Sat Dec 10 16:36:01 CET 2011

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
overwritten by the kernel.

Reported-by: Paul Kot <pawlkt at gmail.com>
Signed-off-by: Sven Eckelmann <sven at narfation.org>
Marek pointed out that it is better to merge patch 1 and 2. I think it doesn't
make sense to leave Paul Kot as author because it doesn't look like his patch
at all.

And thanks to Andrew for s/overridden/overwritten/

 icmp_socket.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/icmp_socket.c b/icmp_socket.c
index 5bc8649..66923d2 100644
--- a/icmp_socket.c
+++ b/icmp_socket.c
@@ -136,10 +136,9 @@ static ssize_t bat_socket_read(struct file *file, char __user *buf,
-	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;
 	if (error)

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