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 ABC3650B8B1; Tue, 13 Oct 2026 12:05:42 +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=1791893144; cv=none; b=Z4W6tiJrir1RsiBAi97Ap2Zw9lM94JsVWngGckzLOj1aDka6pm3gkw3CfuYyoiZJjLqIFEQnlGmBBXYcHfVCNt7zAPOqf0Ngg6PrSUhDLFUIZQF+SnpjPzDQdJvL9dXRWGWaG/zJoHyhnbKpHV0pW8P0swiPAoPC4xOgUw92CeE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791893144; c=relaxed/simple; bh=uU8a9LORjTqH11oW6gkvcRyD610yBfzBpw7pMYv86u8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=A+H4HS1k7Fa/koKZ3qJWvm9Xm/jqIqcewacg4kF3q8M4w7viq9OGqK3tmjps/nu2ImUM2T7D9UGt8k8QXV6Gu1eCEtjdKIVIwpOuYPyKXq+1fbxAM9WRhqMa+pzIfhmm3p+jpI4FlAQErgBHhtiV3Q78LeZh35FzOMGBw4W11rk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vjfmJwsg; 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="vjfmJwsg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C83AB1F000FF; Tue, 13 Oct 2026 12:05:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791893142; bh=YFG58IxHKo3hApt7i9ODw1rL2Y3MPbd2OPvt2R7tRpk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=vjfmJwsgRdm2HSDMm9cInS7U+n8ugrtVOk/Wr2A3h40tMNgl5xrvSBOrfIFyn6ynB 0tm/XCb1XC0EO09f+ecNeWy62CTtekDuz+1tx94GZuKqUgtQ1KDk/SNB4cN+bCNCv4 lGW2SY2wPy5pFcksHG1Hh5bfPjWnP+w1ylUwmvY0= 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 6.18 110/621] drm/fb-helper: defer setup when fbdev_probe() fails, not just on -EAGAIN Date: Tue, 13 Oct 2026 13:31:45 +0200 Message-ID: <20261013112923.461084324@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112920.855194808@linuxfoundation.org> References: <20261013112920.855194808@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 6.18-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 @@ -1800,10 +1800,10 @@ __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;