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Tue, 7 Apr 2026 07:47:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id x8C2NJm21GlUbQAAD6G6ig (envelope-from ); Tue, 07 Apr 2026 07:47:37 +0000 Message-ID: Date: Tue, 7 Apr 2026 09:47:37 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/fb-helper: Fix a locking bug in an error path From: Thomas Zimmermann To: Bart Van Assche , Maarten Lankhorst Cc: Maxime Ripard , linux-kernel@vger.kernel.org, =?UTF-8?Q?Christian_K=C3=B6nig?= , Dmitry Baryshkov , Javier Martinez Canillas , David Airlie , Simona Vetter , Nathan Chancellor , dri-devel References: <20260403205355.1181984-1-bvanassche@acm.org> <1c03e4d8-0eac-4863-a18d-1ea750c853fb@suse.de> Content-Language: en-US Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: <1c03e4d8-0eac-4863-a18d-1ea750c853fb@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[11]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[kernel.org,vger.kernel.org,amd.com,oss.qualcomm.com,redhat.com,gmail.com,ffwll.ch,lists.freedesktop.org]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[qualcomm.com:email,suse.com:url,suse.de:mid,suse.de:email,acm.org:email,amd.com:email] X-Spam-Flag: NO X-Spam-Score: -4.30 X-Spam-Level: (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 >> Cc: Christian König # radeon >> Cc: Dmitry Baryshkov # msm >> Cc: Javier Martinez Canillas >> Fixes: 63c971af4036 ("drm/fb-helper: Allocate and release fb_info in >> single place") >> Signed-off-by: Bart Van Assche > > Reviewed-by: Thomas Zimmermann > > 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)