linux-kernel - [PATCH AUTOSEL 6.6 35/40] eventfs: Do not allow NULL parent to eventfs_start

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Message-ID: <20231128210615.875085-35-sashal@kernel.org>
Date:   Tue, 28 Nov 2023 16:05:41 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Josef Bacik <josef@...icpanda.com>,
        Sasha Levin <sashal@...nel.org>,
        linux-trace-kernel@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 35/40] eventfs: Do not allow NULL parent to eventfs_start_creating()

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

[ Upstream commit fc4561226feaad5fcdcb55646c348d77b8ee69c5 ]

The eventfs directory is dynamically created via the meta data supplied by
the existing trace events. All files and directories in eventfs has a
parent. Do not allow NULL to be passed into eventfs_start_creating() as
the parent because that should never happen. Warn if it does.

Link: https://lkml.kernel.org/r/20231121231112.693841807@goodmis.org

Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Josef Bacik <josef@...icpanda.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/tracefs/inode.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 891653ba9cf35..0292c6a2bed9f 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -509,20 +509,15 @@ struct dentry *eventfs_start_creating(const char *name, struct dentry *parent)
 	struct dentry *dentry;
 	int error;
 
+	/* Must always have a parent. */
+	if (WARN_ON_ONCE(!parent))
+		return ERR_PTR(-EINVAL);
+
 	error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
 			      &tracefs_mount_count);
 	if (error)
 		return ERR_PTR(error);
 
-	/*
-	 * If the parent is not specified, we create it in the root.
-	 * We need the root dentry to do this, which is in the super
-	 * block. A pointer to that is in the struct vfsmount that we
-	 * have around.
-	 */
-	if (!parent)
-		parent = tracefs_mount->mnt_root;
-
 	if (unlikely(IS_DEADDIR(parent->d_inode)))
 		dentry = ERR_PTR(-ENOENT);
 	else
-- 
2.42.0