From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (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 C86EE58203 for ; Thu, 21 Mar 2024 07:14:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711005290; cv=none; b=XvsKH4//BNcoI4PfnquDxBGCuirNjEVWwr/L3pyoWlqsFMRYWqyEho6lXsvFChwrbd77KqHU/28doMzJge0+s1JDwc7zqMU7Wj6BHKF88mzsgErsxfcxmSu4vd9EMU9GTOablxKctA4n9FIc+blu234E3gkbmvR2hJrC03OY5AA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711005290; c=relaxed/simple; bh=l1DPPk0G8aT58R7Bkm96noh8Um2KT0ETIyTs1PS22AU=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=hTAgLqQVis2tELEvVVh8zgCcLp5f3cjlZRPsHyaDtfdd3MMYEoHhr1iF9Lntzn+ea3jQlVFga33/oSnNd5BInQko55/2YG+zVI4cgUtaeyRUaFTDWojPLK39r6gxshWvK9RQ5JpKy6hMa5PdCS8frUQ6mPwDEoS4RMwKMkEO7bE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.234]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4V0c9Y2RDrz1xsDD for ; Thu, 21 Mar 2024 15:12:49 +0800 (CST) Received: from kwepemm600013.china.huawei.com (unknown [7.193.23.68]) by mail.maildlp.com (Postfix) with ESMTPS id 216951400CB for ; Thu, 21 Mar 2024 15:14:43 +0800 (CST) Received: from huawei.com (10.175.112.208) by kwepemm600013.china.huawei.com (7.193.23.68) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Thu, 21 Mar 2024 15:14:42 +0800 From: Guo Mengqi To: CC: Subject: [PATCH] drm/vkms: call drm_atomic_helper_shutdown before drm_dev_put() Date: Thu, 21 Mar 2024 15:06:48 +0800 Message-ID: <20240321070648.80673-1-guomengqi3@huawei.com> X-Mailer: git-send-email 2.17.1 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To kwepemm600013.china.huawei.com (7.193.23.68) commit 73a82b22963d ("drm/atomic: Fix potential use-after-free in nonblocking commits") introduced drm_dev_get/put() to drm_atomic_helper_shutdown(). And this cause problem in vkms driver exit process. vkms_exit() drm_dev_put() vkms_release() drm_atomic_helper_shutdown() drm_dev_get() drm_dev_put() vkms_release() ------ null pointer access Using 4.19 stable x86 image on qemu, below stacktrace can be triggered by load and unload vkms.ko. root:~ # insmod vkms.ko [ 142.135449] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013). [ 142.138713] [drm] Driver supports precise vblank timestamp query. [ 142.142390] [drm] Initialized vkms 1.0.0 20180514 for virtual device on minor 0 root:~ # rmmod vkms.ko [ 144.093710] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0 [ 144.097491] PGD 800000023624e067 P4D 800000023624e067 PUD 22ab59067 PMD 0 [ 144.100802] Oops: 0000 [#1] SMP PTI [ 144.102502] CPU: 0 PID: 3615 Comm: rmmod Not tainted 4.19.310 #1 [ 144.104452] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 [ 144.107238] RIP: 0010:device_del+0x34/0x3a0 ... [ 144.131323] Call Trace: [ 144.131962] ? __die+0x7d/0xc0 [ 144.132711] ? no_context+0x152/0x3b0 [ 144.133605] ? wake_up_q+0x70/0x70 [ 144.134436] ? __do_page_fault+0x342/0x4b0 [ 144.135445] ? __switch_to_asm+0x41/0x70 [ 144.136416] ? __switch_to_asm+0x35/0x70 [ 144.137366] ? page_fault+0x1e/0x30 [ 144.138214] ? __drm_atomic_state_free+0x51/0x60 [ 144.139331] ? device_del+0x34/0x3a0 [ 144.140197] platform_device_del.part.14+0x19/0x70 [ 144.141348] platform_device_unregister+0xe/0x20 [ 144.142458] vkms_release+0x10/0x30 [vkms] [ 144.143449] __drm_atomic_helper_disable_all.constprop.31+0x13b/0x150 [ 144.144980] drm_atomic_helper_shutdown+0x4b/0x90 [ 144.146102] vkms_release+0x18/0x30 [vkms] [ 144.147107] vkms_exit+0x29/0x8ec [vkms] [ 144.148053] __x64_sys_delete_module+0x155/0x220 [ 144.149168] do_syscall_64+0x43/0x100 [ 144.150056] entry_SYSCALL_64_after_hwframe+0x5c/0xc1 It seems that the proper unload sequence is: drm_atomic_helper_shutdown(); drm_dev_put(); Just put drm_atomic_helper_shutdown() before drm_dev_put() should solve the problem. Fixes: 73a82b22963d ("drm/atomic: Fix potential use-after-free in nonblocking commits") Signed-off-by: Guo Mengqi --- drivers/gpu/drm/vkms/vkms_drv.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c index b1201c18d3eb..d32e08f17427 100644 --- a/drivers/gpu/drm/vkms/vkms_drv.c +++ b/drivers/gpu/drm/vkms/vkms_drv.c @@ -39,7 +39,6 @@ static void vkms_release(struct drm_device *dev) struct vkms_device *vkms = container_of(dev, struct vkms_device, drm); platform_device_unregister(vkms->platform); - drm_atomic_helper_shutdown(&vkms->drm); drm_mode_config_cleanup(&vkms->drm); drm_dev_fini(&vkms->drm); } @@ -137,6 +136,7 @@ static void __exit vkms_exit(void) } drm_dev_unregister(&vkms_device->drm); + drm_atomic_helper_shutdown(&vkms_device->drm); drm_dev_put(&vkms_device->drm); kfree(vkms_device); -- 2.17.1