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

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

[Gustavo A. R. Silva]

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>
---
 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

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

[Sam Ravnborg]

Hi Gustavo.

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

	Sam

> ---
>  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
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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

[Bartlomiej Zolnierkiewicz]

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:
>> 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
> 
>> ---
>>  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
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://protect2.fireeye.com/url?k{ae4d09-26604cda-7bafc646-000babff317b-7eab3a2caa4b8b73&q=1&u=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Fdri-devel

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

[Bartlomiej Zolnierkiewicz]

On 6/17/20 7:56 PM, Gustavo A. R. Silva wrote:
> 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>

Applied to drm-misc-next tree, thanks.

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

> ---
>  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;
>