PPP: Fix PPP buffer sizing.

This patch addresses the issue with "osize too small" errors in mppe
encryption.  The patch fixes the issue with wrong output buffer size
being passed to ppp decompression routine.

--------------------
As pointed out by Suresh Mahalingam, the issue addressed by
ppp-fix-osize-too-small-errors-when-decoding patch is not fully resolved yet.
The size of allocated output buffer is correct, however it size passed to
ppp->rcomp->decompress in ppp_generic.c if wrong. The patch fixes that.
--------------------
Signed-off-by: Konstantin Sharlaimov <konstantin.sharlaimov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/net/ppp_generic.c

@@ -1726,7 +1726,7 @@ ppp_decompress_frame(struct ppp *ppp, struct sk_buff *skb)
 		}
 		/* the decompressor still expects the A/C bytes in the hdr */
 		len = ppp->rcomp->decompress(ppp->rc_state, skb->data - 2,
-				skb->len + 2, ns->data, ppp->mru + PPP_HDRLEN);
+				skb->len + 2, ns->data, obuff_size);
 		if (len < 0) {
 			/* Pass the compressed frame to pppd as an
 			   error indication. */