linux-kernel - [PATCH] afs: security: Use struct

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Message-ID: <20190109144911.GA11648@embeddedor>
Date:   Wed, 9 Jan 2019 08:49:11 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] afs: security: Use struct_size() in kzalloc()

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 foo {
    int stuff;
    void *entry[];
};

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

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_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 fs/afs/security.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/afs/security.c b/fs/afs/security.c
index 5f58a9a17e69..4e9a6c96b9e8 100644
--- a/fs/afs/security.c
+++ b/fs/afs/security.c
@@ -197,8 +197,7 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
 	 * yet.
 	 */
 	size++;
-	new = kzalloc(sizeof(struct afs_permits) +
-		      sizeof(struct afs_permit) * size, GFP_NOFS);
+	new = kzalloc(struct_size(new, permits, size), GFP_NOFS);
 	if (!new)
 		goto out_put;
 
-- 
2.20.1