[PATCH] gcov: use struct_size() in kzalloc()

[PATCH] gcov: 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 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

Re: [PATCH] gcov: use struct_size() in kzalloc()

[Peter Oberparleiter]

On 09.01.2019 18:24, Gustavo A. R. Silva wrote:
> 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>

Looks sane.

Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>

Andrew, could you pick this patch up?

-- 
Peter Oberparleiter
Linux on Z Development - IBM Germany