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From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] gcov: use struct_size() in kzalloc()
Date: Wed, 9 Jan 2019 11:24:45 -0600
Message-ID: <20190109172445.GA15908@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;
    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@embeddedor.com>
---
 kernel/gcov/gcc_3_4.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/gcov/gcc_3_4.c b/kernel/gcov/gcc_3_4.c
index 1e32e66c9563..2dddecbdbe6e 100644
--- a/kernel/gcov/gcc_3_4.c
+++ b/kernel/gcov/gcc_3_4.c
@@ -245,8 +245,7 @@ struct gcov_info *gcov_info_dup(struct gcov_info *info)
 
 	/* Duplicate gcov_info. */
 	active = num_counter_active(info);
-	dup = kzalloc(sizeof(struct gcov_info) +
-		      sizeof(struct gcov_ctr_info) * active, GFP_KERNEL);
+	dup = kzalloc(struct_size(dup, counts, active), GFP_KERNEL);
 	if (!dup)
 		return NULL;
 	dup->version		= info->version;
@@ -364,8 +363,7 @@ struct gcov_iterator *gcov_iter_new(struct gcov_info *info)
 {
 	struct gcov_iterator *iter;
 
-	iter = kzalloc(sizeof(struct gcov_iterator) +
-		       num_counter_active(info) * sizeof(struct type_info),
+	iter = kzalloc(struct_size(iter, type_info, num_counter_active(info)),
 		       GFP_KERNEL);
 	if (iter)
 		iter->info = info;
-- 
2.20.1


             reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09 17:24 Gustavo A. R. Silva [this message]
2019-01-11 15:59 ` Peter Oberparleiter

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