Re: [PATCH][next] fbdev/fb.h: Use struct_size() helper in kzalloc()

On 6/20/20 1:27 PM, Sam Ravnborg wrote:

Hi Gustavo.

On Wed, Jun 17, 2020 at 12:56:47PM -0500, Gustavo A. R. Silva wrote:

quoted

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes.

This code was detected with the help of Coccinelle and, audited and
fixed manually.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

struct_size is defined in overflow.h - which is not included by fs.h.
So we rely on overflow.h being pulled in by some other header - maybe
slab.h in this case.
Seems fragile, should this patch add an include of overflow.h?

$ git grep struct_size drivers/|wc -l
697

$ git grep overflow\\.h drivers/|wc -l
8

$ git grep overflow\\.h include/linux/
include/linux/device.h:#include <linux/overflow.h>
include/linux/mm.h:#include <linux/overflow.h>
include/linux/slab.h:#include <linux/overflow.h>
include/linux/vmalloc.h:#include <linux/overflow.h>

so I've applied the patch as it is (hoping that the issue is so
widespread that no-one tries to remove overflow.h from slab.h
without fixing drivers at the same time)..

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

	Sam

quoted

---
 include/linux/fb.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/fb.h b/include/linux/fb.h
index 3b4b2f0c6994..2b530e6d86e4 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h

@@ -506,8 +506,9 @@ struct fb_info {
 };
 
 static inline struct apertures_struct *alloc_apertures(unsigned int max_num) {
-	struct apertures_struct *a = kzalloc(sizeof(struct apertures_struct)
-			+ max_num * sizeof(struct aperture), GFP_KERNEL);
+	struct apertures_struct *a;
+
+	a = kzalloc(struct_size(a, ranges, max_num), GFP_KERNEL);
 	if (!a)
 		return NULL;
 	a->count = max_num;

-- 
2.27.0

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