linux-kernel - Re: [PATCH v3] ACPI: platform-profile: Fix CFI violation when accessing sysfs files

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Message-ID: <2025021105-simply-stubbed-1744@gregkh>
Date: Tue, 11 Feb 2025 07:27:31 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Mark Pearson <mpearson-lenovo@...ebb.ca>,
	Mario Limonciello <mario.limonciello@....com>,
	Kees Cook <kees@...nel.org>,
	Sami Tolvanen <samitolvanen@...gle.com>, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
	patches@...ts.linux.dev, stable@...r.kernel.org,
	John Rowley <lkml@...nrowley.me>
Subject: Re: [PATCH v3] ACPI: platform-profile: Fix CFI violation when
 accessing sysfs files

On Mon, Feb 10, 2025 at 09:28:25PM -0500, Nathan Chancellor wrote:
> When an attribute group is created with sysfs_create_group(), the
> ->sysfs_ops() callback is set to kobj_sysfs_ops, which sets the ->show()
> and ->store() callbacks to kobj_attr_show() and kobj_attr_store()
> respectively. These functions use container_of() to get the respective
> callback from the passed attribute, meaning that these callbacks need to
> be the same type as the callbacks in 'struct kobj_attribute'.
> 
> However, the platform_profile sysfs functions have the type of the
> ->show() and ->store() callbacks in 'struct device_attribute', which
> results a CFI violation when accessing platform_profile or
> platform_profile_choices under /sys/firmware/acpi because the types do
> not match:
> 
>   CFI failure at kobj_attr_show+0x19/0x30 (target: platform_profile_choices_show+0x0/0x140; expected type: 0x7a69590c)
> 
> There is no functional issue from the type mismatch because the layout
> of 'struct kobj_attribute' and 'struct device_attribute' are the same,
> so the container_of() cast does not break anything aside from CFI.
> 
> Change the type of platform_profile_choices_show() and
> platform_profile_{show,store}() to match the callbacks in
> 'struct kobj_attribute' and update the attribute variables to match,
> which resolves the CFI violation.

Nice catch.

> Cc: stable@...r.kernel.org
> Fixes: a2ff95e018f1 ("ACPI: platform: Add platform profile support")
> Reported-by: John Rowley <lkml@...nrowley.me>
> Closes: https://github.com/ClangBuiltLinux/linux/issues/2047
> Tested-by: John Rowley <lkml@...nrowley.me>
> Reviewed-by: Sami Tolvanen <samitolvanen@...gle.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> Changes in v3:
> - Rebase on 6.14-rc1, which includes updates to the driver to address
>   Greg's previous concerns but this change is still needed for the
>   legacy sysfs interface. v2 can be used for the stable backport.
> - Link to v2: https://lore.kernel.org/r/20241118-acpi-platform_profile-fix-cfi-violation-v2-1-62ff952804de@kernel.org

I'll never find that, so be prepared for a "FAILED" email when this hits
Linus's tree :)

Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>