[PATCH] ima: ima_api: Use struct_size() in kzalloc()

[Gustavo A. R. Silva]

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct ima_template_entry {
        ...
        struct ima_field_data template_data[0]; /* template related data */
};

instance = kzalloc(sizeof(struct ima_template_entry) + count * sizeof(struct 
ima_field_data), GFP_NOFS);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_NOFS);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gust...@embeddedor.com>
---
 security/integrity/ima/ima_api.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 65224474675b..610759fe63b8 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -45,8 +45,8 @@ int ima_alloc_init_template(struct ima_event_data *event_data,
        else
                template_desc = ima_template_desc_current();
 
-       *entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
-                        sizeof(struct ima_field_data), GFP_NOFS);
+       *entry = kzalloc(struct_size(*entry, template_data,
+                                    template_desc->num_fields), GFP_NOFS);
        if (!*entry)
                return -ENOMEM;
 
-- 
2.23.0