linux-kernel - Re: [PATCH] drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <202211020843.A19F75B@keescook>
Date:   Wed, 2 Nov 2022 08:43:27 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Stefan Agner <stefan@...er.ch>, Alison Wang <alison.wang@....com>,
        dri-devel@...ts.freedesktop.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Sami Tolvanen <samitolvanen@...gle.com>, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH] drm/fsl-dcu: Fix return type of
 fsl_dcu_drm_connector_mode_valid()

On Wed, Nov 02, 2022 at 08:42:15AM -0700, Nathan Chancellor wrote:
> With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
> indirect call targets are validated against the expected function
> pointer prototype to make sure the call target is valid to help mitigate
> ROP attacks. If they are not identical, there is a failure at run time,
> which manifests as either a kernel panic or thread getting killed. A
> proposed warning in clang aims to catch these at compile time, which
> reveals:
> 
>   drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c:74:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict]
>           .mode_valid = fsl_dcu_drm_connector_mode_valid,
>                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   1 error generated.
> 
> ->mode_valid() in 'struct drm_connector_helper_funcs' expects a return
> type of 'enum drm_mode_status', not 'int'. Adjust the return type of
> fsl_dcu_drm_connector_mode_valid() to match the prototype's to resolve
> the warning and CFI failure.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1750
> Reported-by: Sami Tolvanen <samitolvanen@...gle.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook