Re: [PATCH] drm/fb-helper: Fix a locking bug in an error path

[Thomas Zimmermann]

Hi

Am 03.04.26 um 22:53 schrieb Bart Van Assche:
> The name of the function __drm_fb_helper_initial_config_and_unlock() and
> also the comment above that function make it clear that all code paths
> in this function should unlock fb_helper->lock before returning. Add a
> mutex_unlock() call in the only code path where it is missing. This has
> been detected by the Clang thread-safety analyzer.
>
> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Cc: Christian König <christian.koenig@xxxxxxx> # radeon
> Cc: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx> # msm
> Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx>
> Fixes: 63c971af4036 ("drm/fb-helper: Allocate and release fb_info in single place")
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>

Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>

Thanks a lot.

Best regards
Thomas

> ---
>   drivers/gpu/drm/drm_fb_helper.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 05803169bed5..16bfbfb0af16 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1641,8 +1641,10 @@ __drm_fb_helper_initial_config_and_unlock(struct drm_fb_helper *fb_helper)
>   	drm_client_modeset_probe(&fb_helper->client, width, height);
>   
>   	info = drm_fb_helper_alloc_info(fb_helper);
> -	if (IS_ERR(info))
> +	if (IS_ERR(info)) {
> +		mutex_unlock(&fb_helper->lock);
>   		return PTR_ERR(info);
> +	}
>   
>   	ret = drm_fb_helper_single_fb_probe(fb_helper);
>   	if (ret < 0) {

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)