[PATCH v3] ath9k: dfs: Remove VLA usage

[PATCH v3] ath9k: dfs: Remove VLA usage

[Kees Cook]

In the quest to remove all stack VLA usage from the kernel[1], this
redefines FFT_NUM_SAMPLES as a #define instead of const int, which still
triggers gcc's VLA checking pass.

[1] https://lkml.org/lkml/2018/3/7/621

Co-developed-by: Andreas Christoforou <andreaschristofo@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v3: replace FFT_NUM_SAMPLES as a #define (Joe)
---
 drivers/net/wireless/ath/ath9k/dfs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/dfs.c b/drivers/net/wireless/ath/ath9k/dfs.c
index 6fee9a464cce..e6e56a925121 100644
--- a/drivers/net/wireless/ath/ath9k/dfs.c
+++ b/drivers/net/wireless/ath/ath9k/dfs.c
@@ -40,8 +40,8 @@ static const int BIN_DELTA_MIN		= 1;
 static const int BIN_DELTA_MAX		= 10;
 
 /* we need at least 3 deltas / 4 samples for a reliable chirp detection */
-#define NUM_DIFFS 3
-static const int FFT_NUM_SAMPLES	= (NUM_DIFFS + 1);
+#define NUM_DIFFS	3
+#define FFT_NUM_SAMPLES	(NUM_DIFFS + 1)
 
 /* Threshold for difference of delta peaks */
 static const int MAX_DIFF		= 2;
-- 
2.7.4


-- 
Kees Cook
Pixel Security

Re: [PATCH v3] ath9k: dfs: Remove VLA usage

[Kalle Valo]

Kees Cook <keescook@chromium.org> writes:

> In the quest to remove all stack VLA usage from the kernel[1], this
> redefines FFT_NUM_SAMPLES as a #define instead of const int, which still
> triggers gcc's VLA checking pass.
>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Co-developed-by: Andreas Christoforou <andreaschristofo@gmail.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> v3: replace FFT_NUM_SAMPLES as a #define (Joe)
> ---
>  drivers/net/wireless/ath/ath9k/dfs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath9k/dfs.c
> b/drivers/net/wireless/ath/ath9k/dfs.c
> index 6fee9a464cce..e6e56a925121 100644
> --- a/drivers/net/wireless/ath/ath9k/dfs.c
> +++ b/drivers/net/wireless/ath/ath9k/dfs.c
> @@ -40,8 +40,8 @@ static const int BIN_DELTA_MIN		= 1;
>  static const int BIN_DELTA_MAX		= 10;
>  
>  /* we need at least 3 deltas / 4 samples for a reliable chirp detection */
> -#define NUM_DIFFS 3
> -static const int FFT_NUM_SAMPLES	= (NUM_DIFFS + 1);
> +#define NUM_DIFFS	3
> +#define FFT_NUM_SAMPLES	(NUM_DIFFS + 1)

I have already applied an almost identical patch:

ath9k: dfs: remove accidental use of stack VLA

https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=ath-next&id=9c27489a34548913baaaf3b2776e05d4a9389e3e

-- 
Kalle Valo

Re: [PATCH v3] ath9k: dfs: Remove VLA usage

[Kees Cook]

On Wed, Apr 25, 2018 at 12:26 AM, Kalle Valo <kvalo@codeaurora.org> wrote:
> I have already applied an almost identical patch:
>
> ath9k: dfs: remove accidental use of stack VLA
>
> https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=ath-next&id=9c27489a34548913baaaf3b2776e05d4a9389e3e

Ah! Cool, no worries. I didn't see that in linux-next yet. :)

Thanks!

-Kees

-- 
Kees Cook
Pixel Security