[SCTP]: Fix warning

An alternate solution would be to make the digest a pointer, allocate
it in sctp_endpoint_init() and free it in sctp_endpoint_destroy().

I guess I should have originally done it this way...

  CC [M]  net/sctp/sm_make_chunk.o
net/sctp/sm_make_chunk.c: In function 'sctp_unpack_cookie':
net/sctp/sm_make_chunk.c:1358: warning: initialization discards qualifiers from pointer target type

The reason is that sctp_unpack_cookie() takes a const struct
sctp_endpoint and modifies the digest in it (digest being embedded in
the struct, not a pointer).  Make digest a pointer to fix this
warning.
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

@@ -1270,7 +1270,7 @@ struct sctp_endpoint {
  	 * 	    this here so we pre-allocate this once and can re-use
  	 * 	    on every receive.
  	 */
- 	__u8 digest[SCTP_SIGNATURE_SIZE];
+ 	__u8 *digest;
  
 	/* sendbuf acct. policy.	*/
 	__u32 sndbuf_policy;

net/sctp/endpointola.c

@@ -72,6 +72,10 @@ static struct sctp_endpoint *sctp_endpoint_init(struct sctp_endpoint *ep,
 {
 	memset(ep, 0, sizeof(struct sctp_endpoint));
 
+	ep->digest = kzalloc(SCTP_SIGNATURE_SIZE, gfp);
+	if (!ep->digest)
+		return NULL;
+
 	/* Initialize the base structure. */
 	/* What type of endpoint are we?  */
 	ep->base.type = SCTP_EP_TYPE_SOCKET;
@@ -182,6 +186,9 @@ static void sctp_endpoint_destroy(struct sctp_endpoint *ep)
 	/* Free up the HMAC transform. */
 	crypto_free_hash(sctp_sk(ep->base.sk)->hmac);
 
+	/* Free the digest buffer */
+	kfree(ep->digest);
+
 	/* Cleanup. */
 	sctp_inq_free(&ep->base.inqueue);
 	sctp_bind_addr_free(&ep->base.bind_addr);