NetLabel: fixup the handling of CIPSOv4 tags to allow for multiple tag types

While the original CIPSOv4 code had provisions for multiple tag types the
implementation was not as great as it could be, pushing a lot of non-tag
specific processing into the tag specific code blocks.  This patch fixes that
issue making it easier to support multiple tag types in the future.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>

net/ipv4/cipso_ipv4.c

@@ -958,35 +958,28 @@ static int cipso_v4_map_cat_rbm_ntoh(const struct cipso_v4_doi *doi_def,
  * Protocol Handling Functions
  */
 
+#define CIPSO_V4_OPT_LEN_MAX          40
 #define CIPSO_V4_HDR_LEN              6
 
 /**
  * cipso_v4_gentag_hdr - Generate a CIPSO option header
  * @doi_def: the DOI definition
- * @len: the total tag length in bytes
+ * @len: the total tag length in bytes, not including this header
  * @buf: the CIPSO option buffer
  *
  * Description:
- * Write a CIPSO header into the beginning of @buffer.  Return zero on success,
- * negative values on failure.
+ * Write a CIPSO header into the beginning of @buffer.
  *
  */
-static int cipso_v4_gentag_hdr(const struct cipso_v4_doi *doi_def,
-			       u32 len,
-			       unsigned char *buf)
+static void cipso_v4_gentag_hdr(const struct cipso_v4_doi *doi_def,
+				unsigned char *buf,
+				u32 len)
 {
-	if (CIPSO_V4_HDR_LEN + len > 40)
-		return -ENOSPC;
-
 	buf[0] = IPOPT_CIPSO;
 	buf[1] = CIPSO_V4_HDR_LEN + len;
 	*(__be32 *)&buf[2] = htonl(doi_def->doi);
-
-	return 0;
 }
 
-#define CIPSO_V4_TAG1_CAT_LEN         30
-
 /**
  * cipso_v4_gentag_rbm - Generate a CIPSO restricted bitmap tag (type #1)
  * @doi_def: the DOI definition
@@ -997,71 +990,50 @@ static int cipso_v4_gentag_hdr(const struct cipso_v4_doi *doi_def,
  * Description:
  * Generate a CIPSO option using the restricted bitmap tag, tag type #1.  The
  * actual buffer length may be larger than the indicated size due to
- * translation between host and network category bitmaps.  Returns zero on
- * success, negative values on failure.
+ * translation between host and network category bitmaps.  Returns the size of
+ * the tag on success, negative values on failure.
  *
  */
 static int cipso_v4_gentag_rbm(const struct cipso_v4_doi *doi_def,
 			       const struct netlbl_lsm_secattr *secattr,
-			       unsigned char **buffer,
-			       u32 *buffer_len)
+			       unsigned char *buffer,
+			       u32 buffer_len)
 {
 	int ret_val;
-	unsigned char *buf = NULL;
-	u32 buf_len;
+	u32 tag_len;
 	u32 level;
 
 	if ((secattr->flags & NETLBL_SECATTR_MLS_LVL) == 0)
 		return -EPERM;
 
-	if (secattr->flags & NETLBL_SECATTR_MLS_CAT) {
-		buf = kzalloc(CIPSO_V4_HDR_LEN + 4 + CIPSO_V4_TAG1_CAT_LEN,
-			      GFP_ATOMIC);
-		if (buf == NULL)
-			return -ENOMEM;
+	ret_val = cipso_v4_map_lvl_hton(doi_def, secattr->mls_lvl, &level);
+	if (ret_val != 0)
+		return ret_val;
 
+	if (secattr->flags & NETLBL_SECATTR_MLS_CAT) {
 		ret_val = cipso_v4_map_cat_rbm_hton(doi_def,
 						    secattr->mls_cat,
 						    secattr->mls_cat_len,
-						    &buf[CIPSO_V4_HDR_LEN + 4],
-						    CIPSO_V4_TAG1_CAT_LEN);
+						    &buffer[4],
+						    buffer_len - 4);
 		if (ret_val < 0)
-			goto gentag_failure;
+			return ret_val;
 
 		/* This will send packets using the "optimized" format when
 		 * possibile as specified in  section 3.4.2.6 of the
 		 * CIPSO draft. */
 		if (cipso_v4_rbm_optfmt && ret_val > 0 && ret_val <= 10)
-			buf_len = 14;
+			tag_len = 14;
 		else
-			buf_len = 4 + ret_val;
-	} else {
-		buf = kzalloc(CIPSO_V4_HDR_LEN + 4, GFP_ATOMIC);
-		if (buf == NULL)
-			return -ENOMEM;
-		buf_len = 4;
-	}
-
-	ret_val = cipso_v4_map_lvl_hton(doi_def, secattr->mls_lvl, &level);
-	if (ret_val != 0)
-		goto gentag_failure;
-
-	ret_val = cipso_v4_gentag_hdr(doi_def, buf_len, buf);
-	if (ret_val != 0)
-		goto gentag_failure;
-
-	buf[CIPSO_V4_HDR_LEN] = 0x01;
-	buf[CIPSO_V4_HDR_LEN + 1] = buf_len;
-	buf[CIPSO_V4_HDR_LEN + 3] = level;
+			tag_len = 4 + ret_val;
+	} else
+		tag_len = 4;
 
-	*buffer = buf;
-	*buffer_len = CIPSO_V4_HDR_LEN + buf_len;
+	buffer[0] = 0x01;
+	buffer[1] = tag_len;
+	buffer[3] = level;
 
-	return 0;
-
-gentag_failure:
-	kfree(buf);
-	return ret_val;
+	return tag_len;
 }
 
 /**
@@ -1284,7 +1256,7 @@ int cipso_v4_socket_setattr(const struct socket *sock,
 {
 	int ret_val = -EPERM;
 	u32 iter;
-	unsigned char *buf = NULL;
+	unsigned char *buf;
 	u32 buf_len = 0;
 	u32 opt_len;
 	struct ip_options *opt = NULL;
@@ -1300,17 +1272,28 @@ int cipso_v4_socket_setattr(const struct socket *sock,
 	if (sk == NULL)
 		return 0;
 
+	/* We allocate the maximum CIPSO option size here so we are probably
+	 * being a little wasteful, but it makes our life _much_ easier later
+	 * on and after all we are only talking about 40 bytes. */
+	buf_len = CIPSO_V4_OPT_LEN_MAX;
+	buf = kmalloc(buf_len, GFP_ATOMIC);
+	if (buf == NULL) {
+		ret_val = -ENOMEM;
+		goto socket_setattr_failure;
+	}
+
 	/* XXX - This code assumes only one tag per CIPSO option which isn't
 	 * really a good assumption to make but since we only support the MAC
 	 * tags right now it is a safe assumption. */
 	iter = 0;
 	do {
+		memset(buf, 0, buf_len);
 		switch (doi_def->tags[iter]) {
 		case CIPSO_V4_TAG_RBITMAP:
 			ret_val = cipso_v4_gentag_rbm(doi_def,
-						      secattr,
-						      &buf,
-						      &buf_len);
+						   secattr,
+						   &buf[CIPSO_V4_HDR_LEN],
+						   buf_len - CIPSO_V4_HDR_LEN);
 			break;
 		default:
 			ret_val = -EPERM;
@@ -1318,11 +1301,13 @@ int cipso_v4_socket_setattr(const struct socket *sock,
 		}
 
 		iter++;
-	} while (ret_val != 0 &&
+	} while (ret_val < 0 &&
 		 iter < CIPSO_V4_TAG_MAXCNT &&
 		 doi_def->tags[iter] != CIPSO_V4_TAG_INVALID);
-	if (ret_val != 0)
+	if (ret_val < 0)
 		goto socket_setattr_failure;
+	cipso_v4_gentag_hdr(doi_def, buf, ret_val);
+	buf_len = CIPSO_V4_HDR_LEN + ret_val;
 
 	/* We can't use ip_options_get() directly because it makes a call to
 	 * ip_options_get_alloc() which allocates memory with GFP_KERNEL and
@@ -1396,6 +1381,10 @@ int cipso_v4_sock_getattr(struct sock *sk, struct netlbl_lsm_secattr *secattr)
 		rcu_read_unlock();
 		return -ENOMSG;
 	}
+
+	/* XXX - This code assumes only one tag per CIPSO option which isn't
+	 * really a good assumption to make but since we only support the MAC
+	 * tags right now it is a safe assumption. */
 	switch (cipso_ptr[6]) {
 	case CIPSO_V4_TAG_RBITMAP:
 		ret_val = cipso_v4_parsetag_rbm(doi_def,
@@ -1458,6 +1447,10 @@ int cipso_v4_skbuff_getattr(const struct sk_buff *skb,
 	doi_def = cipso_v4_doi_getdef(doi);
 	if (doi_def == NULL)
 		goto skbuff_getattr_return;
+
+	/* XXX - This code assumes only one tag per CIPSO option which isn't
+	 * really a good assumption to make but since we only support the MAC
+	 * tags right now it is a safe assumption. */
 	switch (cipso_ptr[6]) {
 	case CIPSO_V4_TAG_RBITMAP:
 		ret_val = cipso_v4_parsetag_rbm(doi_def,