ima: allocate field pointers array on demand in template_desc_init_fields()

The allocation of a field pointers array is moved at the end of
template_desc_init_fields() and done only if the value of the 'fields'
and 'num_fields' parameters is not NULL. For just validating a template
format string, retrieved template field pointers are placed in a temporary
array.

Changelog:
 - v3:
   - do not check in this patch if 'fields' and 'num_fields' are NULL
     (suggested by Mimi Zohar)

Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index d93a58e603df2c0acdc50cbdb30ae37f8088822e..65117ba06809685b346476db20b4e358e96c2baf 100644 (file)
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -117,8 +117,9 @@ static int template_desc_init_fields(const char *template_fmt,
                                     int *num_fields)
 {
        const char *template_fmt_ptr;
+       struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
        int template_num_fields = template_fmt_size(template_fmt);
-       int i, len, result = 0;
+       int i, len;
 
        if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
                pr_err("format string '%s' contains too many fields\n",
@@ -126,41 +127,32 @@ static int template_desc_init_fields(const char *template_fmt,
                return -EINVAL;
        }
 
-       *fields = kzalloc(template_num_fields * sizeof(*fields), GFP_KERNEL);
-       if (*fields == NULL) {
-               result = -ENOMEM;
-               goto out;
-       }
-
        for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
             i++, template_fmt_ptr += len + 1) {
                char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];
-               struct ima_template_field *f;
 
                len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
                if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
                        pr_err("Invalid field with length %d\n", len);
-                       result = -EINVAL;
-                       goto out;
+                       return -EINVAL;
                }
 
                memcpy(tmp_field_id, template_fmt_ptr, len);
                tmp_field_id[len] = '\0';
-               f = lookup_template_field(tmp_field_id);
-               if (!f) {
+               found_fields[i] = lookup_template_field(tmp_field_id);
+               if (!found_fields[i]) {
                        pr_err("field '%s' not found\n", tmp_field_id);
-                       result = -ENOENT;
-                       goto out;
+                       return -ENOENT;
                }
-               (*fields)[i] = f;
        }
+
+       *fields = kmalloc_array(i, sizeof(*fields), GFP_KERNEL);
+       if (*fields == NULL)
+               return -ENOMEM;
+
+       memcpy(*fields, found_fields, i * sizeof(*fields));
        *num_fields = i;
-out:
-       if (result < 0) {
-               kfree(*fields);
-               *fields = NULL;
-       }
-       return result;
+       return 0;
 }
 
 struct ima_template_desc *ima_template_desc_current(void)