linux-kernel - [PATCH 4.9 21/29] tracefs: Set the group ownership in apply_options() not parse

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Message-Id: <20220228172143.892637061@linuxfoundation.org>
Date:   Mon, 28 Feb 2022 18:23:48 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>
Subject: [PATCH 4.9 21/29] tracefs: Set the group ownership in apply_options() not parse_options()

From: Steven Rostedt (Google) <rostedt@...dmis.org>

commit 851e99ebeec3f4a672bb5010cf1ece095acee447 upstream.

Al Viro brought it to my attention that the dentries may not be filled
when the parse_options() is called, causing the call to set_gid() to
possibly crash. It should only be called if parse_options() succeeds
totally anyway.

He suggested the logical place to do the update is in apply_options().

Link: https://lore.kernel.org/all/20220225165219.737025658@goodmis.org/
Link: https://lkml.kernel.org/r/20220225153426.1c4cab6b@gandalf.local.home

Cc: stable@...r.kernel.org
Acked-by: Al Viro <viro@...iv.linux.org.uk>
Reported-by: Al Viro <viro@...iv.linux.org.uk>
Fixes: 48b27b6b5191 ("tracefs: Set all files to the same group ownership as the mount option")
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/tracefs/inode.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -265,7 +265,6 @@ static int tracefs_parse_options(char *d
 			if (!gid_valid(gid))
 				return -EINVAL;
 			opts->gid = gid;
-			set_gid(tracefs_mount->mnt_root, gid);
 			break;
 		case Opt_mode:
 			if (match_octal(&args[0], &option))
@@ -292,7 +291,9 @@ static int tracefs_apply_options(struct
 	inode->i_mode |= opts->mode;
 
 	inode->i_uid = opts->uid;
-	inode->i_gid = opts->gid;
+
+	/* Set all the group ids to the mount option */
+	set_gid(sb->s_root, opts->gid);
 
 	return 0;
 }