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 module_notes_attrs.

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

Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: linux-modules@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 kernel/module/sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/module/sysfs.c b/kernel/module/sysfs.c
index c921bf044050..d964167c6658 100644
--- a/kernel/module/sysfs.c
+++ b/kernel/module/sysfs.c
@@ -143,7 +143,7 @@ static void remove_sect_attrs(struct module *mod)
 struct module_notes_attrs {
 	struct kobject *dir;
 	unsigned int notes;
-	struct bin_attribute attrs[];
+	struct bin_attribute attrs[] __counted_by(notes);
 };
 
 static ssize_t module_notes_read(struct file *filp, struct kobject *kobj,
-- 
2.34.1

On Fri, Sep 22, 2023 at 10:52:53AM -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 module_notes_attrs.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Luis Chamberlain <mcgrof@kernel.org>
> Cc: linux-modules@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
--
Gustavo

> ---
>  kernel/module/sysfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/module/sysfs.c b/kernel/module/sysfs.c
> index c921bf044050..d964167c6658 100644
> --- a/kernel/module/sysfs.c
> +++ b/kernel/module/sysfs.c
> @@ -143,7 +143,7 @@ static void remove_sect_attrs(struct module *mod)
>  struct module_notes_attrs {
>  	struct kobject *dir;
>  	unsigned int notes;
> -	struct bin_attribute attrs[];
> +	struct bin_attribute attrs[] __counted_by(notes);
>  };
>  
>  static ssize_t module_notes_read(struct file *filp, struct kobject *kobj,
> -- 
> 2.34.1
> 
>