linux-kernel - [PATCH 5.15 11/69] drm/simpledrm: Fix return type of simpledrm_simple_display_pipe_mode

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Message-Id: <20220801114134.942362731@linuxfoundation.org>
Date:   Mon,  1 Aug 2022 13:46:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Tomasz Paweł Gajc <tpgxyz@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH 5.15 11/69] drm/simpledrm: Fix return type of simpledrm_simple_display_pipe_mode_valid()

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

commit 0c09bc33aa8e9dc867300acaadc318c2f0d85a1e upstream.

When booting a kernel compiled with clang's CFI protection
(CONFIG_CFI_CLANG), there is a CFI failure in
drm_simple_kms_crtc_mode_valid() when trying to call
simpledrm_simple_display_pipe_mode_valid() through ->mode_valid():

[    0.322802] CFI failure (target: simpledrm_simple_display_pipe_mode_valid+0x0/0x8):
...
[    0.324928] Call trace:
[    0.324969]  __ubsan_handle_cfi_check_fail+0x58/0x60
[    0.325053]  __cfi_check_fail+0x3c/0x44
[    0.325120]  __cfi_slowpath_diag+0x178/0x200
[    0.325192]  drm_simple_kms_crtc_mode_valid+0x58/0x80
[    0.325279]  __drm_helper_update_and_validate+0x31c/0x464
...

The ->mode_valid() member in 'struct drm_simple_display_pipe_funcs'
expects a return type of 'enum drm_mode_status', not 'int'. Correct it
to fix the CFI failure.

Cc: stable@...r.kernel.org
Fixes: 11e8f5fd223b ("drm: Add simpledrm driver")
Link: https://github.com/ClangBuiltLinux/linux/issues/1647
Reported-by: Tomasz Paweł Gajc <tpgxyz@...il.com>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Thomas Zimmermann <tzimmermann@...e.de>
Reviewed-by: Sami Tolvanen <samitolvanen@...gle.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220725233629.223223-1-nathan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/tiny/simpledrm.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -614,7 +614,7 @@ static const struct drm_connector_funcs
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static int
+static enum drm_mode_status
 simpledrm_simple_display_pipe_mode_valid(struct drm_simple_display_pipe *pipe,
 				    const struct drm_display_mode *mode)
 {