2019-01-08 16:01:10

by Gustavo A. R. Silva

Subject: [PATCH] mtd: gen_probe: Use struct_size() in kmalloc()

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 <[email protected]>
---
drivers/mtd/chips/gen_probe.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/chips/gen_probe.c b/drivers/mtd/chips/gen_probe.c
index 837b04ab96a9..839ed40625d6 100644
--- a/drivers/mtd/chips/gen_probe.c
+++ b/drivers/mtd/chips/gen_probe.c
@@ -135,7 +135,7 @@ static struct cfi_private *genprobe_ident_chips(struct map_info *map, struct chi
* our caller, and copy the appropriate data into them.
*/

- retcfi = kmalloc(sizeof(struct cfi_private) + cfi.numchips * sizeof(struct flchip), GFP_KERNEL);
+ retcfi = kmalloc(struct_size(retcfi, chips, cfi.numchips), GFP_KERNEL);

if (!retcfi) {
kfree(cfi.cfiq);
--
2.20.1

2019-01-16 18:30:38

by Boris Brezillon

Subject: Re: mtd: gen_probe: Use struct_size() in kmalloc()

From: Boris Brezillon <[email protected]>

On Tue, 2019-01-08 at 15:36:01 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 = 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 <[email protected]>

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

Boris