Hi

Am 26.07.22 um 02:12 schrieb Sami Tolvanen:

On Mon, Jul 25, 2022 at 4:37 PM Nathan Chancellor nathan@kernel.org 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@vger.kernel.org Fixes: 11e8f5fd223b ("drm: Add simpledrm driver") Link: https://github.com/ClangBuiltLinux/linux/issues/1647 Reported-by: Tomasz Paweł Gajc tpgxyz@gmail.com Signed-off-by: Nathan Chancellor nathan@kernel.org

---

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@google.com

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

Best regards Thomas

Sami