From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9050BC56205 for ; Thu, 6 Aug 2026 17:00:20 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7827510E0B7; Thu, 6 Aug 2026 17:00:19 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=linux.dev header.i=@linux.dev header.b="h1NOLEL2"; dkim-atps=neutral Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) by gabe.freedesktop.org (Postfix) with ESMTPS id B996410E0B7 for ; Thu, 6 Aug 2026 17:00:16 +0000 (UTC) Message-ID: <03ebefdc-9324-47f4-adff-12b5e94b8840@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1786035614; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PkIgPRKZrNMDtQHsZmMZ+wAcfVEh2PjQ1HO2Xs2ueYg=; b=h1NOLEL2fjo55DwEtk58Gr+zSabHMozJwbA+HXQ0Zx+FfKgbz/rjkVpk7oQ62DiFqM4Qe/ +TjTryDzyBm7nsQJJOOiGw7DMwLiy7Nx7FT5SCld8QQahArd7tWnKXtwUxSJlShD/zkoaX ZDPp9dkeapKHp/v/VZM11TUIvKr2+9U= Date: Fri, 7 Aug 2026 00:59:23 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v2 9/9] drm/debugfs: hold device reference for the lifetime of open files To: Danilo Krummrich , Alice Ryhl , Daniel Almeida Cc: Miguel Ojeda , Boqun Feng , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , =?UTF-8?Q?Onur_=C3=96zkan?= , Greg Kroah-Hartman , "Rafael J. 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From: Alvin Sun In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 8/4/26 01:56, Danilo Krummrich wrote: > On Thu Jul 30, 2026 at 7:05 PM CEST, Alvin Sun wrote: >> Hold a device reference (via drm_dev_get/put) across the lifetime of open >> debugfs files. Prevents use-after-free when a device is unregistered while >> a debugfs file remains open. Both drm_debugfs_open (legacy info_list) >> and drm_debugfs_entry_open (drm_debugfs_add_file) paths are covered. >> >> Fixes: 1c9cacbea8805 ("drm/debugfs: create device-centered debugfs functions") >> Fixes: 28a62277e06f9 ("drm: Convert proc files to seq_file and introduce debugfs") >> >> Signed-off-by: Alvin Sun >> --- >> drivers/gpu/drm/drm_debugfs.c | 42 ++++++++++++++++++++++++++++++++++++++---- >> 1 file changed, 38 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c >> index 38cf6ce387cc8..5262a708f1602 100644 >> --- a/drivers/gpu/drm/drm_debugfs.c >> +++ b/drivers/gpu/drm/drm_debugfs.c >> @@ -159,11 +159,28 @@ static const struct drm_debugfs_info drm_debugfs_list[] = { >> static int drm_debugfs_open(struct inode *inode, struct file *file) >> { >> struct drm_info_node *node = inode->i_private; >> + struct drm_device *dev = node->minor->dev; >> + int ret; >> >> if (!device_is_registered(node->minor->kdev)) >> return -ENODEV; >> >> - return single_open(file, node->info_ent->show, node); >> + drm_dev_get(dev); >> + >> + ret = single_open(file, node->info_ent->show, node); >> + if (ret) >> + drm_dev_put(dev); >> + >> + return ret; >> +} >> + >> +static int drm_debugfs_release(struct inode *inode, struct file *file) >> +{ >> + struct drm_info_node *node = >> + ((struct seq_file *)file->private_data)->private; >> + >> + drm_dev_put(node->minor->dev); >> + return single_release(inode, file); >> } > This isn't needed; in drm_dev_unregister() we call debugfs_remove_recursive(), > which already waits for all in-flight file operations. The DRM device itself is > guaranteed to be valid as long as it is registered. Thanks for the review. Sorry for the delay — I was on vacation the last few days. v3 is ready, incorporating the feedback, and I'll send it out shortly. Best regards, Alvin