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

Gustavo A. R. Silva
2019-06-05T14:45:22Z

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