Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct ep93xx_dma_engine.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Vinod Koul <vkoul@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tom Rix <trix@redhat.com>
Cc: dmaengine@vger.kernel.org
Cc: llvm@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/dma/ep93xx_dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
index 5c4a448a1254..d6c60635e90d 100644
--- a/drivers/dma/ep93xx_dma.c
+++ b/drivers/dma/ep93xx_dma.c
@@ -213,7 +213,7 @@ struct ep93xx_dma_engine {
 #define INTERRUPT_NEXT_BUFFER	2
 
 	size_t			num_channels;
-	struct ep93xx_dma_chan	channels[];
+	struct ep93xx_dma_chan	channels[] __counted_by(num_channels);
 };
 
 static inline struct device *chan2dev(struct ep93xx_dma_chan *edmac)
-- 
2.34.1

On Thu, 28 Sep 2023 16:43:42 -0700, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct ep93xx_dma_engine.
> 
> [...]

Applied, thanks!

[1/1] dmaengine: ep93xx_dma: Annotate struct ep93xx_dma_engine with __counted_by
      commit: 74d885711c2f619e92f41ef308691948cc63f224

Best regards,
-- 
~Vinod

On 9/29/23 01:43, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct ep93xx_dma_engine.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Vinod Koul <vkoul@kernel.org>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Tom Rix <trix@redhat.com>
> Cc: dmaengine@vger.kernel.org
> Cc: llvm@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
-- 
Gustavo

> ---
>   drivers/dma/ep93xx_dma.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
> index 5c4a448a1254..d6c60635e90d 100644
> --- a/drivers/dma/ep93xx_dma.c
> +++ b/drivers/dma/ep93xx_dma.c
> @@ -213,7 +213,7 @@ struct ep93xx_dma_engine {
>   #define INTERRUPT_NEXT_BUFFER	2
>   
>   	size_t			num_channels;
> -	struct ep93xx_dma_chan	channels[];
> +	struct ep93xx_dma_chan	channels[] __counted_by(num_channels);
>   };
>   
>   static inline struct device *chan2dev(struct ep93xx_dma_chan *edmac)