From nobody Mon Apr 6 09:41:24 2026 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 2F5CAC54EE9 for ; Thu, 8 Sep 2022 21:12:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229981AbiIHVMv (ORCPT ); Thu, 8 Sep 2022 17:12:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229926AbiIHVMl (ORCPT ); Thu, 8 Sep 2022 17:12:41 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0107FE125D; Thu, 8 Sep 2022 14:12:40 -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 ams.source.kernel.org (Postfix) with ESMTPS id AC3E5B8229B; Thu, 8 Sep 2022 21:12:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 631BFC43470; Thu, 8 Sep 2022 21:12:38 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.96) (envelope-from ) id 1oWOps-00DB4i-2p; Thu, 08 Sep 2022 17:13:20 -0400 Message-ID: <20220908211320.708265647@goodmis.org> User-Agent: quilt/0.66 Date: Thu, 08 Sep 2022 17:13:04 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , stable@vger.kernel.org, Brian Norris Subject: [for-linus][PATCH 2/2] tracefs: Only clobber mode/uid/gid on remount if asked References: <20220908211302.262245973@goodmis.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Brian Norris Users may have explicitly configured their tracefs permissions; we shouldn't overwrite those just because a second mount appeared. Only clobber if the options were provided at mount time. Note: the previous behavior was especially surprising in the presence of automounted /sys/kernel/debug/tracing/. Existing behavior: ## Pre-existing status: tracefs is 0755. # stat -c '%A' /sys/kernel/tracing/ drwxr-xr-x ## (Re)trigger the automount. # umount /sys/kernel/debug/tracing # stat -c '%A' /sys/kernel/debug/tracing/. drwx------ ## Unexpected: the automount changed mode for other mount instances. # stat -c '%A' /sys/kernel/tracing/ drwx------ New behavior (after this change): ## Pre-existing status: tracefs is 0755. # stat -c '%A' /sys/kernel/tracing/ drwxr-xr-x ## (Re)trigger the automount. # umount /sys/kernel/debug/tracing # stat -c '%A' /sys/kernel/debug/tracing/. drwxr-xr-x ## Expected: the automount does not change other mount instances. # stat -c '%A' /sys/kernel/tracing/ drwxr-xr-x Link: https://lkml.kernel.org/r/20220826174353.2.Iab6e5ea57963d6deca5311b27= fb7226790d44406@changeid Cc: stable@vger.kernel.org Fixes: 4282d60689d4f ("tracefs: Add new tracefs file system") Signed-off-by: Brian Norris Signed-off-by: Steven Rostedt (Google) --- fs/tracefs/inode.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 81d26abf486f..da85b3979195 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -141,6 +141,8 @@ struct tracefs_mount_opts { kuid_t uid; kgid_t gid; umode_t mode; + /* Opt_* bitfield. */ + unsigned int opts; }; =20 enum { @@ -241,6 +243,7 @@ static int tracefs_parse_options(char *data, struct tra= cefs_mount_opts *opts) kgid_t gid; char *p; =20 + opts->opts =3D 0; opts->mode =3D TRACEFS_DEFAULT_MODE; =20 while ((p =3D strsep(&data, ",")) !=3D NULL) { @@ -275,24 +278,36 @@ static int tracefs_parse_options(char *data, struct t= racefs_mount_opts *opts) * but traditionally tracefs has ignored all mount options */ } + + opts->opts |=3D BIT(token); } =20 return 0; } =20 -static int tracefs_apply_options(struct super_block *sb) +static int tracefs_apply_options(struct super_block *sb, bool remount) { struct tracefs_fs_info *fsi =3D sb->s_fs_info; struct inode *inode =3D d_inode(sb->s_root); struct tracefs_mount_opts *opts =3D &fsi->mount_opts; =20 - inode->i_mode &=3D ~S_IALLUGO; - inode->i_mode |=3D opts->mode; + /* + * On remount, only reset mode/uid/gid if they were provided as mount + * options. + */ + + if (!remount || opts->opts & BIT(Opt_mode)) { + inode->i_mode &=3D ~S_IALLUGO; + inode->i_mode |=3D opts->mode; + } =20 - inode->i_uid =3D opts->uid; + if (!remount || opts->opts & BIT(Opt_uid)) + inode->i_uid =3D opts->uid; =20 - /* Set all the group ids to the mount option */ - set_gid(sb->s_root, opts->gid); + if (!remount || opts->opts & BIT(Opt_gid)) { + /* Set all the group ids to the mount option */ + set_gid(sb->s_root, opts->gid); + } =20 return 0; } @@ -307,7 +322,7 @@ static int tracefs_remount(struct super_block *sb, int = *flags, char *data) if (err) goto fail; =20 - tracefs_apply_options(sb); + tracefs_apply_options(sb, true); =20 fail: return err; @@ -359,7 +374,7 @@ static int trace_fill_super(struct super_block *sb, voi= d *data, int silent) =20 sb->s_op =3D &tracefs_super_operations; =20 - tracefs_apply_options(sb); + tracefs_apply_options(sb, false); =20 return 0; =20 --=20 2.35.1