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: NJ. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/auth_gss/gss_krb5_seal.c

@@ -76,7 +76,8 @@ gss_get_mic_kerberos(struct gss_ctx *gss_ctx, struct xdr_buf *text,
 {
 	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 @@ gss_get_mic_kerberos(struct gss_ctx *gss_ctx, struct xdr_buf *text,
 		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 @@ gss_get_mic_kerberos(struct gss_ctx *gss_ctx, struct xdr_buf *text,
 
 	return ((ctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
 out_err:
-	kfree(md5cksum.data);
 	return GSS_S_FAILURE;
 }

net/sunrpc/auth_gss/gss_krb5_unseal.c

@@ -79,7 +79,8 @@ gss_verify_mic_kerberos(struct gss_ctx *gss_ctx,
 	int			signalg;
 	int			sealalg;
 	s32			checksum_type;
-	struct xdr_netobj	md5cksum = {.len = 0, .data = NULL};
+	char			cksumdata[16];
+	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
 	s32			now;
 	int			direction;
 	s32			seqnum;
@@ -176,6 +177,5 @@ gss_verify_mic_kerberos(struct gss_ctx *gss_ctx,
 
 	ret = GSS_S_COMPLETE;
 out:
-	kfree(md5cksum.data);
 	return ret;
 }

net/sunrpc/auth_gss/gss_krb5_wrap.c

@@ -121,7 +121,8 @@ gss_wrap_kerberos(struct gss_ctx *ctx, int offset,
 {
 	struct krb5_ctx		*kctx = 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};
 	int			blocksize = 0, plainlen;
 	unsigned char		*ptr, *krb5_hdr, *msg_start;
 	s32			now;
@@ -205,8 +206,6 @@ gss_wrap_kerberos(struct gss_ctx *ctx, int offset,
 		BUG();
 	}
 
-	kfree(md5cksum.data);
-
 	/* XXX would probably be more efficient to compute checksum
 	 * and encrypt at the same time: */
 	if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
@@ -221,7 +220,6 @@ gss_wrap_kerberos(struct gss_ctx *ctx, int offset,
 
 	return ((kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
 out_err:
-	if (md5cksum.data) kfree(md5cksum.data);
 	return GSS_S_FAILURE;
 }
 
@@ -232,7 +230,8 @@ gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
 	int			signalg;
 	int			sealalg;
 	s32			checksum_type;
-	struct xdr_netobj	md5cksum = {.len = 0, .data = NULL};
+	char			cksumdata[16];
+	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
 	s32			now;
 	int			direction;
 	s32			seqnum;
@@ -358,6 +357,5 @@ gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
 
 	ret = GSS_S_COMPLETE;
 out:
-	if (md5cksum.data) kfree(md5cksum.data);
 	return ret;
 }

net/sunrpc/auth_gss/gss_spkm3_seal.c

@@ -57,7 +57,8 @@ spkm3_make_token(struct spkm3_ctx *ctx,
 {
 	s32			checksum_type;
 	char			tokhdrbuf[25];
-	struct xdr_netobj	md5cksum = {.len = 0, .data = NULL};
+	char			cksumdata[16];
+	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
 	struct xdr_netobj	mic_hdr = {.len = 0, .data = tokhdrbuf};
 	int			tokenlen = 0;
 	unsigned char		*ptr;
@@ -115,13 +116,11 @@ spkm3_make_token(struct spkm3_ctx *ctx,
 		dprintk("RPC: gss_spkm3_seal: SPKM_WRAP_TOK not supported\n");
 		goto out_err;
 	}
-	kfree(md5cksum.data);
 
 	/* XXX need to implement sequence numbers, and ctx->expired */
 
 	return  GSS_S_COMPLETE;
 out_err:
-	kfree(md5cksum.data);
 	token->data = NULL;
 	token->len = 0;
 	return GSS_S_FAILURE;

net/sunrpc/auth_gss/gss_spkm3_unseal.c

@@ -56,7 +56,8 @@ spkm3_read_token(struct spkm3_ctx *ctx,
 {
 	s32			code;
 	struct xdr_netobj	wire_cksum = {.len =0, .data = NULL};
-	struct xdr_netobj	md5cksum = {.len = 0, .data = NULL};
+	char			cksumdata[16];
+	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
 	unsigned char		*ptr = (unsigned char *)read_token->data;
 	unsigned char           *cksum;
 	int			bodysize, md5elen;
@@ -120,7 +121,6 @@ spkm3_read_token(struct spkm3_ctx *ctx,
 	/* XXX: need to add expiration and sequencing */
 	ret = GSS_S_COMPLETE;
 out:
-	kfree(md5cksum.data);
 	kfree(wire_cksum.data);
 	return ret;
 }