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

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Message-ID: <CABCJKue4NgOVxfjcU=oE23rogqgfiiJMqLHp-NSoSs=o1=22kg@mail.gmail.com>
Date: Mon, 19 Aug 2024 14:23:49 -0700
From: Sami Tolvanen <samitolvanen@...gle.com>
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 <markpearson@...ovo.com>, 
	Kees Cook <kees@...nel.org>, 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] ACPI: platform-profile: Fix CFI violation when accessing
 sysfs files

Hi Nathan,

On Mon, Aug 19, 2024 at 12:09 PM Nathan Chancellor <nathan@...nel.org> 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)
>
> This happens to work because the layout of 'struct kobj_attribute' and
> 'struct device_attribute' are the same, so the container_of() cast
> happens to allow the callbacks to still work.
>
> 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.
>
> 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>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>  drivers/acpi/platform_profile.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)

Looks good to me, thanks for fixing this!

Reviewed-by: Sami Tolvanen <samitolvanen@...gle.com>

Sami