2021-09-11 11:28:50

by Len Baker

Subject: [PATCH] Input: omap-keypad - prefer struct_size over open coded arithmetic

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + count * size" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <[email protected]>
---
drivers/input/keyboard/omap-keypad.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/input/keyboard/omap-keypad.c b/drivers/input/keyboard/omap-keypad.c
index dbe836c7ff47..eb3a687796e7 100644
--- a/drivers/input/keyboard/omap-keypad.c
+++ b/drivers/input/keyboard/omap-keypad.c
@@ -190,8 +190,7 @@ static int omap_kp_probe(struct platform_device *pdev)
row_shift = get_count_order(pdata->cols);
keycodemax = pdata->rows << row_shift;

- omap_kp = kzalloc(sizeof(struct omap_kp) +
- keycodemax * sizeof(unsigned short), GFP_KERNEL);
+ omap_kp = kzalloc(struct_size(omap_kp, keymap, keycodemax), GFP_KERNEL);
input_dev = input_allocate_device();
if (!omap_kp || !input_dev) {
kfree(omap_kp);
--
2.25.1

2021-09-14 22:13:42

by Gustavo A. R. Silva

Subject: Re: [PATCH] Input: omap-keypad - prefer struct_size over open coded arithmetic

On 9/11/21 06:27, Len Baker wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, use the struct_size() helper to do the arithmetic instead of the
> argument "size + count * size" in the kzalloc() function.
>
> [1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <[email protected]>

Reviewed-by: Gustavo A. R. Silva <[email protected]>

Thanks
--
Gustavo

> ---
> drivers/input/keyboard/omap-keypad.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/input/keyboard/omap-keypad.c b/drivers/input/keyboard/omap-keypad.c
> index dbe836c7ff47..eb3a687796e7 100644
> --- a/drivers/input/keyboard/omap-keypad.c
> +++ b/drivers/input/keyboard/omap-keypad.c
> @@ -190,8 +190,7 @@ static int omap_kp_probe(struct platform_device *pdev)
> row_shift = get_count_order(pdata->cols);
> keycodemax = pdata->rows << row_shift;
>
> - omap_kp = kzalloc(sizeof(struct omap_kp) +
> - keycodemax * sizeof(unsigned short), GFP_KERNEL);
> + omap_kp = kzalloc(struct_size(omap_kp, keymap, keycodemax), GFP_KERNEL);
> input_dev = input_allocate_device();
> if (!omap_kp || !input_dev) {
> kfree(omap_kp);
> --
> 2.25.1
>
>
>
>