2019-01-08 18:56:10

by Gustavo A. R. Silva

Subject: [PATCH] powerpc/spufs: 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]>
---
arch/powerpc/platforms/cell/spufs/file.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index ae8123edddc6..48c2477e7e2a 100644
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -2338,9 +2338,8 @@ static int spufs_switch_log_open(struct inode *inode, struct file *file)
goto out;
}

- ctx->switch_log = kmalloc(sizeof(struct switch_log) +
- SWITCH_LOG_BUFSIZE * sizeof(struct switch_log_entry),
- GFP_KERNEL);
+ ctx->switch_log = kmalloc(struct_size(ctx->switch_log, log,
+ SWITCH_LOG_BUFSIZE), GFP_KERNEL);

if (!ctx->switch_log) {
rc = -ENOMEM;
--
2.20.1

2019-01-24 03:41:02

by Michael Ellerman

Subject: Re: powerpc/spufs: use struct_size() in kmalloc()

On Tue, 2019-01-08 at 18:37:20 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 powerpc next, thanks.

https://git.kernel.org/powerpc/c/00def7130af8b3fad1bdef98429c94a6

cheers