linux-kernel - [PATCH AUTOSEL 6.0 19/73] drm/meson: Fix return type of meson_encoder_cvbs_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: <20221218160741.927862-19-sashal@kernel.org>
Date:   Sun, 18 Dec 2022 11:06:47 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Sasha Levin <sashal@...nel.org>, airlied@...il.com,
        daniel@...ll.ch, khilman@...libre.com, ndesaulniers@...gle.com,
        dri-devel@...ts.freedesktop.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, llvm@...ts.linux.dev
Subject: [PATCH AUTOSEL 6.0 19/73] drm/meson: Fix return type of meson_encoder_cvbs_mode_valid()

From: Nathan Chancellor <nathan@...nel.org>

[ Upstream commit 6c4e4d35203301906afb53c6d1e1302d4c793c05 ]

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/meson/meson_encoder_cvbs.c:211:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_bridge *, const struct drm_display_info *, const struct drm_display_mode *)' with an expression of type 'int (struct drm_bridge *, const struct drm_display_info *, const struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict]
          .mode_valid = meson_encoder_cvbs_mode_valid,
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  1 error generated.

->mode_valid() in 'struct drm_bridge_funcs' expects a return type of
'enum drm_mode_status', not 'int'. Adjust the return type of
meson_encoder_cvbs_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>
Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221102155242.1927166-1-nathan@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/meson/meson_encoder_cvbs.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/meson/meson_encoder_cvbs.c b/drivers/gpu/drm/meson/meson_encoder_cvbs.c
index 5675bc2a92cf..3f73b211fa8e 100644
--- a/drivers/gpu/drm/meson/meson_encoder_cvbs.c
+++ b/drivers/gpu/drm/meson/meson_encoder_cvbs.c
@@ -116,9 +116,10 @@ static int meson_encoder_cvbs_get_modes(struct drm_bridge *bridge,
 	return i;
 }
 
-static int meson_encoder_cvbs_mode_valid(struct drm_bridge *bridge,
-					const struct drm_display_info *display_info,
-					const struct drm_display_mode *mode)
+static enum drm_mode_status
+meson_encoder_cvbs_mode_valid(struct drm_bridge *bridge,
+			      const struct drm_display_info *display_info,
+			      const struct drm_display_mode *mode)
 {
 	if (meson_cvbs_get_mode(mode))
 		return MODE_OK;
-- 
2.35.1