Re: [PATCH v3 03/13] fs/resctrl: Avoid "may be used uninitialized" warning

[Borislav Petkov]

On Tue, Apr 07, 2026 at 09:02:00AM -0700, Reinette Chatre wrote:
> Building resctrl with extra checks ("W=12") produces the following warning:
>  .../include/linux/ucopysize.h:22:17: warning: ‘buf’ may be used uninitialized [-Wmaybe-uninitialized]
>    22 |                 __check_object_size(ptr, n, to_user);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  .../include/linux/ucopysize.h: In function ‘pseudo_lock_measure_trigger’:
>  .../include/linux/ucopysize.h:10:13: note: by argument 1 of type ‘const void *’ to ‘__check_object_size’ declared here
>    10 | extern void __check_object_size(const void *ptr, unsigned long n,
>       |             ^~~~~~~~~~~~~~~~~~~
>  .../fs/resctrl/pseudo_lock.c:754:14: note: ‘buf’ declared here
>   754 |         char buf[32];
>       |              ^~~
> 
> __check_object_size() ensures the provided buffer is within a valid location
> but does not read from the uninitialized buffer. Even so, initialize the
> buffer to silence the warning to help resctrl have a cleaner build.
> 
> Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
> ---
>  fs/resctrl/pseudo_lock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/resctrl/pseudo_lock.c b/fs/resctrl/pseudo_lock.c
> index fa3687d69ebd..e1e9134474f4 100644
> --- a/fs/resctrl/pseudo_lock.c
> +++ b/fs/resctrl/pseudo_lock.c
> @@ -750,8 +750,8 @@ static ssize_t pseudo_lock_measure_trigger(struct file *file,
>  					   size_t count, loff_t *ppos)
>  {
>  	struct rdtgroup *rdtgrp = file->private_data;
> +	char buf[32] = {};

AFAIU, you're not leaking any uninitialized stack data from that buffer,
right?

If so, why do you care about some silly build warning and are willing to waste
a 32-byte memset on every function entry?

There's a reason those warnings are behind W= ...

:-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette