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 30B4F3B1029; Sat, 12 Sep 2026 18:35:51 +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=1789238157; cv=none; b=UGBpNohFBxFSszjV+6tivWD/wuhi5MHpVdT4eftHxPt/EPrYf+Wa+wg9d/HeIL8w3WdAJo6dea/+X2siBs18kbjB/gsOtNgyNFOdh7E1ZXr387XFLDMczj2OI1Ag+6upZHjQJAorZnHyEVhB/2zPg4nAyrOVP/N/pUSOfibRTrY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789238157; c=relaxed/simple; bh=6uMCDVGChAxDv3GTYu57POdVS7JbSAe93gGT9AoV9+0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TzwLIxB6FlCpOlwF25S6JTsMPyvogRoWuHvvj9E4ntFSu5wrWQxXI/X258SvSu9GxCirzQexKHorRjzSMoZIDZcNiPhWdPVJH52Y8o07lF0FyIxGY2CqzGcg/9UfYIbB/mgw+iF5WYXSrhBMg3zMII0khV4Y47VbCm76hyXPVGE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2fVGrDkG; 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="2fVGrDkG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DCB7C1F000FF; Sat, 12 Sep 2026 18:35:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789238148; bh=Jg85CbKJiETk09w+QIfLXXRFfms66asOYYYpHcbVOOA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=2fVGrDkG/W9FDMpVcdxeelftfi4ej1OuG3Es/KejKWM45w9r45wmft1MVAtVWm1+6 fjzBO0cW2M0nN37G6yPVrP20EjJisszAI4l4xXf5A1pm1n3LA97bPhrrQ/59BydfQM LD3JRgnjEuH3dfm5ejz046d5PKEBMIMdsoVm0lX4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, sashiko-bot@kernel.org, Alexandre Courbot , Lyude Paul , Deborah Brouwer , Danilo Krummrich Subject: [PATCH 5.15 360/935] drm: fix race between partial drm_dev_register() failure and ioctl Date: Sat, 12 Sep 2026 08:56:30 +0200 Message-ID: <20260912065535.063531385@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065526.833703348@linuxfoundation.org> References: <20260912065526.833703348@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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Danilo Krummrich commit eb197f7d60f00d0f5b1b3505dfc86a7e36045a3e upstream. If drm_dev_register() fails after registering a minor (e.g. render minor registered, primary minor fails), userspace could have opened the first minor and entered a drm_dev_enter() critical section. Since the unplugged flag was never set, the ioctl proceeds while the error path tears down device resources. Fix this by introducing drm_dev_synchronize_unplug(), which sets the unplugged flag and waits for the SRCU barrier, ensuring all in-flight drm_dev_enter() critical sections complete before cleanup proceeds; call it on the error path of drm_dev_register(). Fixes: bee330f3d672 ("drm: Use srcu to protect drm_device.unplugged") Cc: stable@vger.kernel.org Reported-by: sashiko-bot@kernel.org Closes: https://lore.kernel.org/all/20260620190648.2E9F61F000E9@smtp.kernel.org/ Reviewed-by: Alexandre Courbot Reviewed-by: Lyude Paul Tested-by: Deborah Brouwer Link: https://patch.msgid.link/20260628145406.2107056-17-dakr@kernel.org Signed-off-by: Danilo Krummrich Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_drv.c | 34 +++++++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 9 deletions(-) --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -448,6 +448,22 @@ void drm_dev_exit(int idx) } EXPORT_SYMBOL(drm_dev_exit); +/* + * Mark the device as unplugged and wait for any in-flight drm_dev_enter() + * critical sections to complete. + */ +static void drm_dev_synchronize_unplug(struct drm_device *dev) +{ + /* + * After synchronizing any critical read section is guaranteed to see + * the new value of ->unplugged, and any critical section which might + * still have seen the old value of ->unplugged is guaranteed to have + * finished. + */ + dev->unplugged = true; + synchronize_srcu(&drm_unplug_srcu); +} + /** * drm_dev_unplug - unplug a DRM device * @dev: DRM device @@ -460,15 +476,7 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) { - /* - * After synchronizing any critical read section is guaranteed to see - * the new value of ->unplugged, and any critical section which might - * still have seen the old value of ->unplugged is guaranteed to have - * finished. - */ - dev->unplugged = true; - synchronize_srcu(&drm_unplug_srcu); - + drm_dev_synchronize_unplug(dev); drm_dev_unregister(dev); /* Clear all CPU mappings pointing to this device */ @@ -887,6 +895,7 @@ int drm_dev_register(struct drm_device * goto err_minors; dev->registered = true; + dev->unplugged = false; if (dev->driver->load) { ret = dev->driver->load(dev, flags); @@ -912,6 +921,13 @@ err_unload: if (dev->driver->unload) dev->driver->unload(dev); err_minors: + /* + * If a minor was registered before the failure, userspace could have + * opened it and entered a drm_dev_enter() critical section. Ensure all + * such sections complete before we clean up. + */ + drm_dev_synchronize_unplug(dev); + remove_compat_control_link(dev); drm_minor_unregister(dev, DRM_MINOR_PRIMARY); drm_minor_unregister(dev, DRM_MINOR_RENDER);