linux-kernel - Re: [PATCH] tee: fix tee_ioctl_object_invoke

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Message-ID: <CAHUa44H1Ejbbuzr1hF1HrT69JGgnvfkkDkh+9KvEvBT+eWBDhw@mail.gmail.com>
Date: Thu, 4 Dec 2025 14:27:46 +0100
From: Jens Wiklander <jens.wiklander@...aro.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, 
	Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>, 
	Sumit Garg <sumit.garg@....qualcomm.com>, Arnd Bergmann <arnd@...db.de>, 
	Sumit Garg <sumit.garg@...nel.org>, Alexandre Ghiti <alex@...ti.fr>, 
	Etienne Carriere <etienne.carriere@...s.st.com>, Randy Dunlap <rdunlap@...radead.org>, 
	op-tee@...ts.trustedfirmware.org, linux-kernel@...r.kernel.org, 
	linux-riscv@...ts.infradead.org
Subject: Re: [PATCH] tee: fix tee_ioctl_object_invoke_arg padding

Hi,

On Thu, Dec 4, 2025 at 11:17 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> The tee_ioctl_object_invoke_arg structure has padding on some
> architectures but not on x86-32 and a few others:
>
> include/linux/tee.h:474:32: error: padding struct to align 'params' [-Werror=padded]
>
> I expect that all current users of this are on architectures that do
> have implicit padding here (arm64, arm, x86, riscv), so make the padding
> explicit in order to avoid surprises if this later gets used elsewhere.
>
> Fixes: d5b8b0fa1775 ("tee: add TEE_IOCTL_PARAM_ATTR_TYPE_OBJREF")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> The new interface showed up in 6.18, but I only came across this after
> that was released. Changing it now is technically an ABI change on
> architectures with unusual padding rules, so please consider carefully
> whether we want to do it this way or not.
>
> Working around the ABI differences without an ABI change is possible,
> but adds a lot of complexity for compat handling.

This is currently only used by the recently introduced qcomtee backend
driver. So it's only used on a few arm64 Qualcomm platforms right now.

I think we should take this patch, but let's hear what others think.

Thanks,
Jens

> ---
>  include/uapi/linux/tee.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/include/uapi/linux/tee.h b/include/uapi/linux/tee.h
> index cab5cadca8ef..5203977ed35d 100644
> --- a/include/uapi/linux/tee.h
> +++ b/include/uapi/linux/tee.h
> @@ -470,6 +470,7 @@ struct tee_ioctl_object_invoke_arg {
>         __u32 op;
>         __u32 ret;
>         __u32 num_params;
> +       __u32 :32;
>         /* num_params tells the actual number of element in params */
>         struct tee_ioctl_param params[];
>  };
> --
> 2.39.5
>