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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F921C88CB4 for ; Tue, 13 Jun 2023 10:23:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241202AbjFMKXB (ORCPT ); Tue, 13 Jun 2023 06:23:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241682AbjFMKWk (ORCPT ); Tue, 13 Jun 2023 06:22:40 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 26F1E1FCB; Tue, 13 Jun 2023 03:22:09 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B3DC060CA5; Tue, 13 Jun 2023 10:22:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A4DC1C433D2; Tue, 13 Jun 2023 10:22:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1686651728; bh=pelskQAIf0QXMoPlaEmAMxMPm+r2Wg28oItNo0pusac=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Tnk4gb9cVZdUkGo5tfNoNWA8VBC1XjEm8bEKOCHKqLCcYJcPFv4xIMCmOYVLG9g5B wU+GjLmg1cmwxV9e4fhSUnvGc2q47IVvIJi8pRIY1bevbSGv416t6T/qektEu0MkWF 9fmqou012AsozmmXKE43gdV9yV182l4gyyJkUxZQ= Date: Tue, 13 Jun 2023 12:22:05 +0200 From: Greg KH To: Alexey Kardashevskiy Cc: Avadhut Naik , rafael@kernel.org, lenb@kernel.org, linux-acpi@vger.kernel.org, linux-fsdevel@vger.kernel.org, avadnaik@amd.com, yazen.ghannam@amd.com, alexey.kardashevskiy@amd.com, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v3 2/3] fs: debugfs: Add write functionality to debugfs blobs Message-ID: <2023061329-splinter-rundown-a61a@gregkh> References: <20230612215139.5132-1-Avadhut.Naik@amd.com> <20230612215139.5132-3-Avadhut.Naik@amd.com> <2023061334-surplus-eclair-197a@gregkh> <1d55a83a-b36a-4319-16bc-c1aa72e361b5@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1d55a83a-b36a-4319-16bc-c1aa72e361b5@amd.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Jun 13, 2023 at 08:05:41PM +1000, Alexey Kardashevskiy wrote: > > > On 13/6/23 17:59, Greg KH wrote: > > On Mon, Jun 12, 2023 at 09:51:38PM +0000, Avadhut Naik wrote: > > > /** > > > - * debugfs_create_blob - create a debugfs file that is used to read a binary blob > > > + * debugfs_create_blob - create a debugfs file that is used to read and write > > > + * a binary blob > > > * @name: a pointer to a string containing the name of the file to create. > > > - * @mode: the read permission that the file should have (other permissions are > > > - * masked out) > > > + * @mode: the permission that the file should have > > > * @parent: a pointer to the parent dentry for this file. This should be a > > > * directory dentry if set. If this parameter is %NULL, then the > > > * file will be created in the root of the debugfs filesystem. > > > @@ -992,7 +1010,7 @@ static const struct file_operations fops_blob = { > > > * > > > * This function creates a file in debugfs with the given name that exports > > > * @blob->data as a binary blob. If the @mode variable is so set it can be > > > - * read from. Writing is not supported. > > > + * read from and written to. > > > * > > > * This function will return a pointer to a dentry if it succeeds. This > > > * pointer must be passed to the debugfs_remove() function when the file is > > > @@ -1007,7 +1025,7 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode, > > > struct dentry *parent, > > > struct debugfs_blob_wrapper *blob) > > > { > > > - return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob); > > > + return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob); > > > > Have you audited all calls to this function to verify that you haven't > > just turned on write access to some debugfs files? > > I just did, it is one of S_IRUGO/S_IRUSR/0444/0400/(S_IFREG | 0444). So we > are quite safe here. Except (S_IFREG | 0444) in > drivers/platform/chrome/cros_ec_debugfs.c which seems wrong as debugfs files > are not regular files. > > > Why not rename this to debugfs_create_blob_wo() and then make a new > > debugfs_create_blob_rw() call to ensure that it all is ok? > > It is already taking the mode for this purpose. imho just > cros_ec_create_panicinfo()'s debugfs_create_blob("panicinfo", S_IFREG | > 0444,...) needs fixing. Yes, well it's taking the mode, but silently modifying it :) Ok, thanks for the audit, respin this with that fix and then I don't have a problem with it (other than binary debugfs files fill me with dread, what could go wrong...) thanks, greg k-h