2019-01-08 15:55:15

by Gustavo A. R. Silva

Subject: [PATCH] mtd: cfi: cmdset_0001: 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/cfi_cmdset_0001.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/chips/cfi_cmdset_0001.c b/drivers/mtd/chips/cfi_cmdset_0001.c
index 6e8e7b1bb34b..79a53cb8507b 100644
--- a/drivers/mtd/chips/cfi_cmdset_0001.c
+++ b/drivers/mtd/chips/cfi_cmdset_0001.c
@@ -756,7 +756,8 @@ static int cfi_intelext_partition_fixup(struct mtd_info *mtd,
}

numvirtchips = cfi->numchips * numparts;
- newcfi = kmalloc(sizeof(struct cfi_private) + numvirtchips * sizeof(struct flchip), GFP_KERNEL);
+ newcfi = kmalloc(struct_size(newcfi, chips, numvirtchips),
+ GFP_KERNEL);
if (!newcfi)
return -ENOMEM;
shared = kmalloc_array(cfi->numchips,
--
2.20.1

2019-01-16 18:30:27

by Boris Brezillon

Subject: Re: mtd: cfi: cmdset_0001: Use struct_size() in kmalloc()

From: Boris Brezillon <[email protected]>

On Tue, 2019-01-08 at 15:52:44 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