* [PATCH] mm: memcontrol: use struct_size() in kmalloc()
@ 2019-01-04 18:37 Gustavo A. R. Silva
2019-01-08 14:52 ` Michal Hocko
2019-01-10 12:12 ` William Kucharski
0 siblings, 2 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2019-01-04 18:37 UTC (permalink / raw)
To: Johannes Weiner, Michal Hocko, Vladimir Davydov
Cc: cgroups, linux-mm, linux-kernel, 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 = kmalloc(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 = kmalloc(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>
---
mm/memcontrol.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index af7f18b32389..ad256cf7da47 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3626,8 +3626,7 @@ static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
size = thresholds->primary ? thresholds->primary->size + 1 : 1;
/* Allocate memory for new array of thresholds */
- new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
- GFP_KERNEL);
+ new = kmalloc(struct_size(new, entries, size), GFP_KERNEL);
if (!new) {
ret = -ENOMEM;
goto unlock;
--
2.20.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm: memcontrol: use struct_size() in kmalloc()
2019-01-04 18:37 [PATCH] mm: memcontrol: use struct_size() in kmalloc() Gustavo A. R. Silva
@ 2019-01-08 14:52 ` Michal Hocko
2019-01-10 12:12 ` William Kucharski
1 sibling, 0 replies; 3+ messages in thread
From: Michal Hocko @ 2019-01-08 14:52 UTC (permalink / raw)
To: Gustavo A. R. Silva
Cc: Johannes Weiner, Vladimir Davydov, cgroups, linux-mm,
linux-kernel, Andrew Morton
Cc Andrew (original patch is here http://lkml.kernel.org/r/20190104183726.GA6374@embeddedor)
On Fri 04-01-19 12:37:26, 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 = kmalloc(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 = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
This looks indeed neater
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Thanks
> ---
> mm/memcontrol.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index af7f18b32389..ad256cf7da47 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3626,8 +3626,7 @@ static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
> size = thresholds->primary ? thresholds->primary->size + 1 : 1;
>
> /* Allocate memory for new array of thresholds */
> - new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
> - GFP_KERNEL);
> + new = kmalloc(struct_size(new, entries, size), GFP_KERNEL);
> if (!new) {
> ret = -ENOMEM;
> goto unlock;
> --
> 2.20.1
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm: memcontrol: use struct_size() in kmalloc()
2019-01-04 18:37 [PATCH] mm: memcontrol: use struct_size() in kmalloc() Gustavo A. R. Silva
2019-01-08 14:52 ` Michal Hocko
@ 2019-01-10 12:12 ` William Kucharski
1 sibling, 0 replies; 3+ messages in thread
From: William Kucharski @ 2019-01-10 12:12 UTC (permalink / raw)
To: Gustavo A. R. Silva
Cc: Johannes Weiner, Michal Hocko, Vladimir Davydov, cgroups,
linux-mm, linux-kernel
> On Jan 4, 2019, at 11:37 AM, Gustavo A. R. Silva <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 foo {
> int stuff;
> void *entry[];
> };
>
> instance = kmalloc(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 = kmalloc(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>
> ---
> mm/memcontrol.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index af7f18b32389..ad256cf7da47 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3626,8 +3626,7 @@ static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
> size = thresholds->primary ? thresholds->primary->size + 1 : 1;
>
> /* Allocate memory for new array of thresholds */
> - new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
> - GFP_KERNEL);
> + new = kmalloc(struct_size(new, entries, size), GFP_KERNEL);
> if (!new) {
> ret = -ENOMEM;
> goto unlock;
> --
> 2.20.1
>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-01-08 14:52 ` Michal Hocko
2019-01-10 12:12 ` William Kucharski
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