linux-kernel - Re: [PATCH] devres: Correclty strip percpu address space of devm_free

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Message-ID: <2024083059-crummy-backrest-3b6c@gregkh>
Date: Fri, 30 Aug 2024 11:54:40 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Uros Bizjak <ubizjak@...il.com>
Cc: linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH] devres: Correclty strip percpu address space of
 devm_free_percpu() argument

On Fri, Aug 30, 2024 at 10:33:52AM +0200, Uros Bizjak wrote:
> devm_free_percpu() calls devres_release() with a pointer in percpu
> address space. devres_release() expects pointers in the generic address
> space, so address space needs to be stripped from the argument.
> 
> When strict percpu address space checks are enabled, then the current
> direct cast from the percpu address space to the generic address space
> fails the compilation on x86_64 with:
> 
> devres.c:1234:32: error: cast to generic address space pointer from disjoint ‘__seg_gs’ address space pointer
> 
> Add intermediate casts to unsigned long to remove address space of
> the pointer before casting it to the generic AS, as advised in [1]
> and [2].
> 
> Side note: sparse still requires __force, although the documentation
> [2] allows casts to unsigned long without __force attribute.
> 
> Found by GCC's named address space checks.
> 
> There were no changes in the resulting object file.
> 
> [1] https://gcc.gnu.org/onlinedocs/gcc/Named-Address-Spaces.html#x86-Named-Address-Spaces
> [2] https://sparse.docs.kernel.org/en/latest/annotations.html#address-space-name
> 
> Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> ---
>  drivers/base/devres.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> index a2ce0ead06a6..2152eec0c135 100644
> --- a/drivers/base/devres.c
> +++ b/drivers/base/devres.c
> @@ -1231,6 +1231,6 @@ void devm_free_percpu(struct device *dev, void __percpu *pdata)
>  	 * devm_free_pages() does.
>  	 */
>  	WARN_ON(devres_release(dev, devm_percpu_release, devm_percpu_match,
> -			       (__force void *)pdata));
> +			       (void *)(__force unsigned long)pdata));
>  }
>  EXPORT_SYMBOL_GPL(devm_free_percpu);
> -- 
> 2.46.0
> 

What commit id does this fix?

thanks,

greg k-h