video: fbdev/mmp/core: Use struct_size() in kzalloc()
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Message ID 20190807161312.GA26835@embeddedor
State New
Headers show
Series
  • video: fbdev/mmp/core: Use struct_size() in kzalloc()
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Commit Message

Gustavo A. R. Silva Aug. 7, 2019, 4:13 p.m. UTC
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 mmp_path {
	...
        struct mmp_overlay overlays[0];
};

size = sizeof(struct mmp_path) + count * sizeof(struct mmp_overlay);
instance = kzalloc(size, 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, overlays, count), GFP_KERNEL)

Notice that, in this case, variable size is not necessary, hence it
is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/video/fbdev/mmp/core.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

Comments

Bartlomiej Zolnierkiewicz Aug. 19, 2019, 2:10 p.m. UTC | #1
On 8/7/19 6:13 PM, 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 mmp_path {
> 	...
>         struct mmp_overlay overlays[0];
> };
> 
> size = sizeof(struct mmp_path) + count * sizeof(struct mmp_overlay);
> instance = kzalloc(size, 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, overlays, count), GFP_KERNEL)
> 
> Notice that, in this case, variable size is not necessary, hence it
> is removed.
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Patch queued for v5.4, thanks.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

Patch
diff mbox series

diff --git a/drivers/video/fbdev/mmp/core.c b/drivers/video/fbdev/mmp/core.c
index 0ffc1b7b7052..154127256a2c 100644
--- a/drivers/video/fbdev/mmp/core.c
+++ b/drivers/video/fbdev/mmp/core.c
@@ -153,13 +153,11 @@  EXPORT_SYMBOL_GPL(mmp_get_path);
 struct mmp_path *mmp_register_path(struct mmp_path_info *info)
 {
 	int i;
-	size_t size;
 	struct mmp_path *path = NULL;
 	struct mmp_panel *panel;
 
-	size = sizeof(struct mmp_path)
-		+ sizeof(struct mmp_overlay) * info->overlay_num;
-	path = kzalloc(size, GFP_KERNEL);
+	path = kzalloc(struct_size(path, overlays, info->overlay_num),
+		       GFP_KERNEL);
 	if (!path)
 		return NULL;