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 cpuinfo_tree.

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

Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/sparc/kernel/cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/sparc/kernel/cpumap.c b/arch/sparc/kernel/cpumap.c
index f07ea88a83af..8fcf2d8c6bd2 100644
--- a/arch/sparc/kernel/cpumap.c
+++ b/arch/sparc/kernel/cpumap.c
@@ -50,7 +50,7 @@ struct cpuinfo_tree {
 
 	/* Offsets into nodes[] for each level of the tree */
 	struct cpuinfo_level level[CPUINFO_LVL_MAX];
-	struct cpuinfo_node  nodes[];
+	struct cpuinfo_node  nodes[] __counted_by(total_nodes);
 };
 
 
-- 
2.34.1

On Fri, 22 Sep 2023 10:52:00 -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 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 cpuinfo_tree.
> 
> [...]

Since this is a trivial change and it's been 2 week without further
discussion, I'll snag this patch.

Applied to for-next/hardening, thanks!

[1/1] sparc: Annotate struct cpuinfo_tree with __counted_by
      https://git.kernel.org/kees/c/cfa36f889f23

Take care,

-- 
Kees Cook

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 cpuinfo_tree.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: sparclinux@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
-- 
Gustavo

> ---
>   arch/sparc/kernel/cpumap.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/sparc/kernel/cpumap.c b/arch/sparc/kernel/cpumap.c
> index f07ea88a83af..8fcf2d8c6bd2 100644
> --- a/arch/sparc/kernel/cpumap.c
> +++ b/arch/sparc/kernel/cpumap.c
> @@ -50,7 +50,7 @@ struct cpuinfo_tree {
>   
>   	/* Offsets into nodes[] for each level of the tree */
>   	struct cpuinfo_level level[CPUINFO_LVL_MAX];
> -	struct cpuinfo_node  nodes[];
> +	struct cpuinfo_node  nodes[] __counted_by(total_nodes);
>   };
>   
>