[PATCH] afs: security: Use struct_size() in kzalloc()

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: David Howells <dhowells@redhat.com>
Cc: linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] afs: security: Use struct_size() in kzalloc()
Date: Tue, 4 Jun 2019 11:29:28 -0500	[thread overview]
Message-ID: <20190604162928.GA12389@embeddedor> (raw)

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;
   struct boo entry[];
};

instance = kzalloc(sizeof(struct foo) + count * sizeof(struct boo), 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@embeddedor.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 71e71c07568f..82753f3c097f 100644
--- a/fs/afs/security.c
+++ b/fs/afs/security.c
@@ -191,8 +191,7 @@ 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;
 
-- 
2.21.0

