2019-01-08 21:11:33

by Gustavo A. R. Silva

Subject: [PATCH] mtd: lpddr: Use struct_size() in kzalloc()

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 <[email protected]>
---
drivers/mtd/lpddr/qinfo_probe.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/lpddr/qinfo_probe.c b/drivers/mtd/lpddr/qinfo_probe.c
index 69f2112340b1..175bdc3b72f4 100644
--- a/drivers/mtd/lpddr/qinfo_probe.c
+++ b/drivers/mtd/lpddr/qinfo_probe.c
@@ -181,8 +181,8 @@ static struct lpddr_private *lpddr_probe_chip(struct map_info *map)
lpddr.numchips = 1;

numvirtchips = lpddr.numchips * lpddr.qinfo->HWPartsNum;
- retlpddr = kzalloc(sizeof(struct lpddr_private) +
- numvirtchips * sizeof(struct flchip), GFP_KERNEL);
+ retlpddr = kzalloc(struct_size(retlpddr, chips, numvirtchips),
+ GFP_KERNEL);
if (!retlpddr)
return NULL;

--
2.20.1

2019-01-16 18:29:28

by Boris Brezillon

Subject: Re: mtd: lpddr: Use struct_size() in kzalloc()

From: Boris Brezillon <[email protected]>

On Tue, 2019-01-08 at 21:09:46 UTC, "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 <[email protected]>

Applied to http://git.infradead.org/linux-mtd.git mtd/next, thanks.

Boris