[PATCH] lib: objagg: Use struct_size() in kzalloc()

[PATCH] lib: objagg: 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 objagg_stats {
	...
        struct objagg_obj_stats_info stats_info[];
};

size = sizeof(*objagg_stats) + sizeof(objagg_stats->stats_info[0]) * count;
instance = kzalloc(size, 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, stats_info, count), GFP_KERNEL);

Notice that, in this case, variable alloc_size is not necessary, hence it
is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 lib/objagg.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/lib/objagg.c b/lib/objagg.c
index 576be22e86de..55621fb82e0a 100644
--- a/lib/objagg.c
+++ b/lib/objagg.c
@@ -605,12 +605,10 @@ const struct objagg_stats *objagg_stats_get(struct objagg *objagg)
 {
 	struct objagg_stats *objagg_stats;
 	struct objagg_obj *objagg_obj;
-	size_t alloc_size;
 	int i;
 
-	alloc_size = sizeof(*objagg_stats) +
-		     sizeof(objagg_stats->stats_info[0]) * objagg->obj_count;
-	objagg_stats = kzalloc(alloc_size, GFP_KERNEL);
+	objagg_stats = kzalloc(struct_size(objagg_stats, stats_info,
+					   objagg->obj_count), GFP_KERNEL);
 	if (!objagg_stats)
 		return ERR_PTR(-ENOMEM);
 
-- 
2.21.0

Re: [PATCH] lib: objagg: Use struct_size() in kzalloc()

[Jiri Pirko]

Wed, Jun 05, 2019 at 04:45:16PM CEST, gustavo@embeddedor.com 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 objagg_stats {
>	...
>        struct objagg_obj_stats_info stats_info[];
>};
>
>size = sizeof(*objagg_stats) + sizeof(objagg_stats->stats_info[0]) * count;
>instance = kzalloc(size, 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, stats_info, count), GFP_KERNEL);
>
>Notice that, in this case, variable alloc_size is not necessary, hence it
>is removed.
>
>This code was detected with the help of Coccinelle.
>
>Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Acked-by: Jiri Pirko <jiri@mellanox.com>

Re: [PATCH] lib: objagg: Use struct_size() in kzalloc()

[David Miller]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Wed, 5 Jun 2019 09:45:16 -0500

> 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 objagg_stats {
> 	...
>         struct objagg_obj_stats_info stats_info[];
> };
> 
> size = sizeof(*objagg_stats) + sizeof(objagg_stats->stats_info[0]) * count;
> instance = kzalloc(size, 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, stats_info, count), GFP_KERNEL);
> 
> Notice that, in this case, variable alloc_size is not necessary, hence it
> is removed.
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Applied.