From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A3EF94F4D0A; Tue, 13 Oct 2026 12:51:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791895884; cv=none; b=O9VEWrFpRbRRclRFDiPDUKTo8RNiUkUQCU//bIs9D7Fat1zliFtUG/6Fb3/U02ErTHv6f7Pg2clCb1uw2QRwfcQkVOvAzKLfTi6stXhpy/KbGCOzyg3KYUOQw/CrIis1oHY1jLPXVOI59g3bj9uBzvLAog6ZQYAsIwD10iGnswY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791895884; c=relaxed/simple; bh=dFCBNq0thWMh2dTC9Gbx0HdEdKonVIDtmpULyCksa2o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=p5h347ikehyEX1Ym+QdORX3ueJd3sWvHSVTGtq1AIHazcZ6ORTm01NDSRhQkCNoyp4L9JX17A+7ZTUoDWEygO4Rnk3A9sYBqQzFIdefDsYSocu36qT7vrl24oeQK204tq6rssTrSbH8+iq1u5ENZhuQWDvbSaHY8MJBBEBpT7os= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=W7aH1i28; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="W7aH1i28" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF8861F00893; Tue, 13 Oct 2026 12:51:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791895883; bh=HDqDnFlQaA+k+zDkw/4yozna3XxQ7kLJuyuKDiT8OF8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=W7aH1i28Mi4i10noF3cDfwEqrMACA74BDWCcVotMFbCIAdD1Mfd6LZcA8dc6vBPJ6 6+p69iIL6rOflxeqGkdi7q6ueNuLwXkfEb7mvc9VCfz0EyUxT9Ji4ySzKmnOY4XN9w MGsH5MJIZbxPyTmPxS6KAUNijAMnC9eMgrIG+TYI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+ca23c8570669ead78867@syzkaller.appspotmail.com, Nguyen Ngoc Thang , Thomas Zimmermann Subject: [PATCH 6.12 426/497] drm/fb-helper: defer setup when fbdev_probe() fails, not just on -EAGAIN Date: Tue, 13 Oct 2026 13:39:53 +0200 Message-ID: <20261013112917.998663330@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112907.864180619@linuxfoundation.org> References: <20261013112907.864180619@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nguyen Ngoc Thang commit 755c94d178b7e972bb766199d34e4ba4f63a89eb upstream. __drm_fb_helper_initial_config_and_unlock() calls drm_client_modeset_probe() first, which already fills in each mode_set->mode/num_connectors for every connected output, and only afterwards calls drm_fb_helper_single_fb_probe() to create fb_helper->fb and wire it into those mode_sets via drm_setup_crtcs_fb(). If drm_fb_helper_single_fb_probe() fails with anything other than -EAGAIN (e.g. dev->driver->fbdev_probe() itself fails), the function bails out before drm_setup_crtcs_fb() runs and before setting fb_helper->deferred_setup. The client is left with mode_sets that have a mode and connectors but mode_set->fb == NULL, and nothing marks this fb_helper as needing a retry. __drm_fb_helper_restore_fbdev_mode_unlocked() only skips committing when fb_helper->deferred_setup is set, so a later .restore() call (drm_lastclose() on process exit, in this report) commits the stale mode_set through drm_client_modeset_commit() -> drm_client_modeset_commit_atomic() -> __drm_atomic_helper_set_config(), which hits WARN_ON(!set->fb). Mark fb_helper->deferred_setup on any drm_fb_helper_single_fb_probe() failure, not just -EAGAIN, so restore keeps skipping the commit until a later hotplug event successfully re-probes and re-populates mode_set->fb. The real error code is still returned to the caller unchanged. Reported-by: syzbot+ca23c8570669ead78867@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=ca23c8570669ead78867 Fixes: ca91a2758fce ("drm/fb-helper: Support deferred setup") Cc: stable@vger.kernel.org Signed-off-by: Nguyen Ngoc Thang Signed-off-by: Thomas Zimmermann Link: https://patch.msgid.link/20260927075434.72658-1-ngocthang2710.1999@gmail.com Link: https://patch.msgid.link/20260917154743.1621-1-shechenglong@xfusion.com Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_fb_helper.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -1790,10 +1790,10 @@ __drm_fb_helper_initial_config_and_unloc ret = drm_fb_helper_single_fb_probe(fb_helper); if (ret < 0) { - if (ret == -EAGAIN) { - fb_helper->deferred_setup = true; + /* modesets are probed but fb_helper->fb isn't; defer restore too */ + fb_helper->deferred_setup = true; + if (ret == -EAGAIN) ret = 0; - } mutex_unlock(&fb_helper->lock); goto err_drm_fb_helper_release_info;