linux-kernel - [PATCH] rhashtable: use struct

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Message-ID: <20190411234306.GA20668@embeddedor>
Date:   Thu, 11 Apr 2019 18:43:06 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Thomas Graf <tgraf@...g.ch>,
        Herbert Xu <herbert@...dor.apana.org.au>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] rhashtable: use struct_size() in kvzalloc()

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[];
};

size = sizeof(struct foo) + count * sizeof(struct boo);
instance = kvzalloc(size, GFP_KERNEL);

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

instance = kvzalloc(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>
---
 lib/rhashtable.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index a8583af43b59..9c84f5cef69c 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -175,8 +175,7 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
 	int i;
 	static struct lock_class_key __key;
 
-	size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
-	tbl = kvzalloc(size, gfp);
+	tbl = kvzalloc(struct_size(tbl, buckets, nbuckets), gfp);
 
 	size = nbuckets;
 
-- 
2.21.0