Re: [PATCH] drm/simpledrm: Fix return type of simpledrm_simple_display_pipe_mode_valid()

Thomas Zimmermann <tzimmermann@xxxxxxx> · Tue, 26 Jul 2022 17:38:44 +0200

Hi

Am 26.07.22 um 02:12 schrieb Sami Tolvanen:
On Mon, Jul 25, 2022 at 4:37 PM Nathan Chancellor <nathan@xxxxxxxxxx> wrote:

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@xxxxxxxxxxxxxxx
Fixes: 11e8f5fd223b ("drm: Add simpledrm driver")
Link: https://github.com/ClangBuiltLinux/linux/issues/1647
Reported-by: Tomasz Paweł Gajc <tpgxyz@xxxxxxxxx>
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
  drivers/gpu/drm/tiny/simpledrm.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
index 768242a78e2b..5422363690e7 100644
--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -627,7 +627,7 @@ static const struct drm_connector_funcs simpledrm_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)
  {

Thanks for fixing this, Nathan! The patch looks correct to me.

Reviewed-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>

Thanks a lot. I've added the patch to drm-misc-fixes.

Best regards
Thomas


Sami

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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