SUNRPC,RPCSEC_GSS: remove unnecessary kmalloc of a checksum

Remove unnecessary kmalloc of temporary space to hold the md5 result; it's
small enough to just put on the stack.

This code may be called to process rpc's necessary to perform writes, so
there's a potential deadlock whenever we kmalloc() here.  After this a
couple kmalloc()'s still remain, to be removed soon.

This also fixes a rare double-free on error noticed by coverity.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/auth_gss/gss_krb5_seal.c b/net/sunrpc/auth_gss/gss_krb5_seal.c
index d0dfdfd..58f9721 100644
--- a/net/sunrpc/auth_gss/gss_krb5_seal.c
+++ b/net/sunrpc/auth_gss/gss_krb5_seal.c
@@ -76,7 +76,8 @@
 {
 	struct krb5_ctx		*ctx = gss_ctx->internal_ctx_id;
 	s32			checksum_type;
-	struct xdr_netobj	md5cksum = {.len = 0, .data = NULL};
+	char			cksumdata[16];
+	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
 	unsigned char		*ptr, *krb5_hdr, *msg_start;
 	s32			now;
 
@@ -133,8 +134,6 @@
 		BUG();
 	}
 
-	kfree(md5cksum.data);
-
 	if ((krb5_make_seq_num(ctx->seq, ctx->initiate ? 0 : 0xff,
 			       ctx->seq_send, krb5_hdr + 16, krb5_hdr + 8)))
 		goto out_err;
@@ -143,6 +142,5 @@
 
 	return ((ctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
 out_err:
-	kfree(md5cksum.data);
 	return GSS_S_FAILURE;
 }