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 checking 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 rtllib_txb.

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

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Cc: linux-staging@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/staging/rtl8192e/rtllib.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8192e/rtllib.h b/drivers/staging/rtl8192e/rtllib.h
index c5a692dfcd17..543d8671281d 100644
--- a/drivers/staging/rtl8192e/rtllib.h
+++ b/drivers/staging/rtl8192e/rtllib.h
@@ -818,7 +818,7 @@ struct rtllib_txb {
 	u16 reserved;
 	__le16 frag_size;
 	__le16 payload_size;
-	struct sk_buff *fragments[];
+	struct sk_buff *fragments[] __counted_by(nr_frags);
 };
 
 #define MAX_SUBFRAME_COUNT		  64
-- 
2.34.1

On 8/17/23 22:45, 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 checking 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 rtllib_txb.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Philipp Hortmann <philipp.g.hortmann@gmail.com>
> Cc: linux-staging@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>   drivers/staging/rtl8192e/rtllib.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/rtl8192e/rtllib.h b/drivers/staging/rtl8192e/rtllib.h
> index c5a692dfcd17..543d8671281d 100644
> --- a/drivers/staging/rtl8192e/rtllib.h
> +++ b/drivers/staging/rtl8192e/rtllib.h
> @@ -818,7 +818,7 @@ struct rtllib_txb {
>   	u16 reserved;
>   	__le16 frag_size;
>   	__le16 payload_size;
> -	struct sk_buff *fragments[];
> +	struct sk_buff *fragments[] __counted_by(nr_frags);
>   };
>   
>   #define MAX_SUBFRAME_COUNT		  64

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>

On 8/17/23 14:45, 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 checking 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 rtllib_txb.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Philipp Hortmann <philipp.g.hortmann@gmail.com>
> Cc: linux-staging@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
--
Gustavo

> ---
>   drivers/staging/rtl8192e/rtllib.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/rtl8192e/rtllib.h b/drivers/staging/rtl8192e/rtllib.h
> index c5a692dfcd17..543d8671281d 100644
> --- a/drivers/staging/rtl8192e/rtllib.h
> +++ b/drivers/staging/rtl8192e/rtllib.h
> @@ -818,7 +818,7 @@ struct rtllib_txb {
>   	u16 reserved;
>   	__le16 frag_size;
>   	__le16 payload_size;
> -	struct sk_buff *fragments[];
> +	struct sk_buff *fragments[] __counted_by(nr_frags);
>   };
>   
>   #define MAX_SUBFRAME_COUNT		  64