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 gcov_iterator.

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

Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 kernel/gcov/fs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/gcov/fs.c b/kernel/gcov/fs.c
index 5c3086cad8f9..01520689b57c 100644
--- a/kernel/gcov/fs.c
+++ b/kernel/gcov/fs.c
@@ -99,7 +99,7 @@ struct gcov_iterator {
 	struct gcov_info *info;
 	size_t size;
 	loff_t pos;
-	char buffer[];
+	char buffer[] __counted_by(size);
 };
 
 /**
-- 
2.34.1

On 22.09.2023 19:52, 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 gcov_iterator.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Looks good to me!

Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>

Andrew, could you add this patch via your tree?


-- 
Peter Oberparleiter
Linux on IBM Z Development - IBM Germany R&D

On 9/22/23 11:52, 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 gcov_iterator.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
-- 
Gustavo

> ---
>   kernel/gcov/fs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/gcov/fs.c b/kernel/gcov/fs.c
> index 5c3086cad8f9..01520689b57c 100644
> --- a/kernel/gcov/fs.c
> +++ b/kernel/gcov/fs.c
> @@ -99,7 +99,7 @@ struct gcov_iterator {
>   	struct gcov_info *info;
>   	size_t size;
>   	loff_t pos;
> -	char buffer[];
> +	char buffer[] __counted_by(size);
>   };
>   
>   /**