[PATCH] kernel: module: Use struct_size() helper

[PATCH] kernel: module: Use struct_size() helper

[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, in particular in the
context in which this code is being used.

So, replace the following form:

sizeof(*sect_attrs) + nloaded * sizeof(sect_attrs->attrs[0]

with:

struct_size(sect_attrs, attrs, nloaded)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 kernel/module.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 80c7c09584cf..3f3bb090fbf4 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1492,8 +1492,7 @@ static void add_sect_attrs(struct module *mod, const struct load_info *info)
 	for (i = 0; i < info->hdr->e_shnum; i++)
 		if (!sect_empty(&info->sechdrs[i]))
 			nloaded++;
-	size[0] = ALIGN(sizeof(*sect_attrs)
-			+ nloaded * sizeof(sect_attrs->attrs[0]),
+	size[0] = ALIGN(struct_size(sect_attrs, attrs, nloaded),
 			sizeof(sect_attrs->grp.attrs[0]));
 	size[1] = (nloaded + 1) * sizeof(sect_attrs->grp.attrs[0]);
 	sect_attrs = kzalloc(size[0] + size[1], GFP_KERNEL);
-- 
2.21.0

Re: [PATCH] kernel: module: Use struct_size() helper

[Jessica Yu]

+++ Gustavo A. R. Silva [04/06/19 18:23 -0500]:
>Make use of the struct_size() helper instead of an open-coded version
>in order to avoid any potential type mistakes, in particular in the
>context in which this code is being used.
>
>So, replace the following form:
>
>sizeof(*sect_attrs) + nloaded * sizeof(sect_attrs->attrs[0]
>
>with:
>
>struct_size(sect_attrs, attrs, nloaded)
>
>This code was detected with the help of Coccinelle.
>
>Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Hi Gustavo!

I see you've sent similar cleanup patches elsewhere, do you think you
could reword your commit message to be more similar to your patch here
for instance:

	https://lkml.org/lkml/2019/6/5/856

It does a *much* better job of explaining the motivation and usage of
struct_size().

Thank you!

Jessica

>---
> kernel/module.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index 80c7c09584cf..3f3bb090fbf4 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -1492,8 +1492,7 @@ static void add_sect_attrs(struct module *mod, const struct load_info *info)
> 	for (i = 0; i < info->hdr->e_shnum; i++)
> 		if (!sect_empty(&info->sechdrs[i]))
> 			nloaded++;
>-	size[0] = ALIGN(sizeof(*sect_attrs)
>-			+ nloaded * sizeof(sect_attrs->attrs[0]),
>+	size[0] = ALIGN(struct_size(sect_attrs, attrs, nloaded),
> 			sizeof(sect_attrs->grp.attrs[0]));
> 	size[1] = (nloaded + 1) * sizeof(sect_attrs->grp.attrs[0]);
> 	sect_attrs = kzalloc(size[0] + size[1], GFP_KERNEL);
>-- 
>2.21.0
>

Re: [PATCH] kernel: module: Use struct_size() helper

[Gustavo A. R. Silva]

Hi Jessica,

On 6/6/19 1:05 PM, Jessica Yu wrote:

> Hi Gustavo!
> 
> I see you've sent similar cleanup patches elsewhere, do you think you
> could reword your commit message to be more similar to your patch here
> for instance:
> 
>     https://lkml.org/lkml/2019/6/5/856
> 
> It does a *much* better job of explaining the motivation and usage of
> struct_size().
> 

Sure thing. :)

I'll send v2 with that change, shortly.

Thanks
--
Gustavo