[ 18/30] ax25: fix info leak via msg_name in ax25_recvmsg()

[Greg Kroah-Hartman]

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

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


From: Mathias Krause <minipli@xxxxxxxxxxxxxx>

[ Upstream commit ef3313e84acbf349caecae942ab3ab731471f1a1 ]

When msg_namelen is non-zero the sockaddr info gets filled out, as
requested, but the code fails to initialize the padding bytes of struct
sockaddr_ax25 inserted by the compiler for alignment. Additionally the
msg_namelen value is updated to sizeof(struct full_sockaddr_ax25) but is
not always filled up to this size.

Both issues lead to the fact that the code will leak uninitialized
kernel stack bytes in net/socket.c.

Fix both issues by initializing the memory with memset(0).

Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ax25/af_ax25.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -1641,6 +1641,7 @@ static int ax25_recvmsg(struct kiocb *io
 		ax25_address src;
 		const unsigned char *mac = skb_mac_header(skb);
 
+		memset(sax, 0, sizeof(struct full_sockaddr_ax25));
 		ax25_addr_parse(mac + 1, skb->data - mac - 1, &src, NULL,
 				&digi, NULL, NULL);
 		sax->sax25_family = AF_AX25;


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