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

[Thomas Zimmermann <tzimmermann@suse.de>]

(cc: dri-devel)

Am 07.04.26 um 09:44 schrieb 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@suse.de>
>> Cc: Christian König <christian.koenig@amd.com> # radeon
>> Cc: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com> # msm
>> Cc: Javier Martinez Canillas <javierm@redhat.com>
>> Fixes: 63c971af4036 ("drm/fb-helper: Allocate and release fb_info in 
>> single place")
>> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
>
> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
>
> 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)