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 DFA524F3922; Tue, 13 Oct 2026 11:52:21 +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=1791892343; cv=none; b=kQrRdFGYAtJtpsPNqOm2klfO2CYnMmR65veL62RBuQxWbq21fFdOeNLKZm9suxpQ4+krb9xCthdy7RY+UazutbwJDyCKblju/8JY8xVuT/l97kqtgw7oeDutgdDH/9sXU2hvinhuWaEVnnGAFgUqaT7RvYpllS5hiymJHykn8dQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791892343; c=relaxed/simple; bh=BS9rxo6ZaszmvpNVkjDbAAyc7FtrNB8YHmRdKxq5tC0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r+oOxRwtp748wkYhCwWD651VBt5ZyNenZ8ofGXm2LpRLFLtzmRMehUlC30mR0xOChwhjq5c6DsOU9Sm3gMtC8VtW9dbenejSHIpRjFyJZnqgApC/82GGJ7ZDbPAwAfRSw4tBWUtpNZiLyZm/8Mz7z3aIdswPWK3KnABTHun53KA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kcDT5ojZ; 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="kcDT5ojZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E64951F0089B; Tue, 13 Oct 2026 11:52:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791892341; bh=eckxmhMilkwUVj9a+Ey8kLciWBZKh7Swyls4SrNvnl8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=kcDT5ojZdL7jbqX4fhYnSN3vTD7W+Vupo/uJAH42ySLE5wGKyONUbd3RPJESMFOFv DgSv56HrFslUV2myu5VAG1hAphm7m47NzwMKx+35D84NntsjUxyh6huZC99c+WXWK3 pUS38UvRnubx4S9XitpbjSWXNuMZW92klFyRucRk= 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 7.2 124/281] drm/fb-helper: defer setup when fbdev_probe() fails, not just on -EAGAIN Date: Tue, 13 Oct 2026 13:37:20 +0200 Message-ID: <20261013112858.159527618@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112855.045212108@linuxfoundation.org> References: <20261013112855.045212108@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 7.2-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 @@ -1724,10 +1724,10 @@ __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;