tracefs: Have tracefs directories not set OTH permission bits by default

The tracefs file system is by default mounted such that only root user can
access it. But there are legitimate reasons to create a group and allow
those added to the group to have access to tracing. By changing the
permissions of the tracefs mount point to allow access, it will allow
group access to the tracefs directory.

There should not be any real reason to allow all access to the tracefs
directory as it contains sensitive information. Have the default
permission of directories being created not have any OTH (other) bits set,
such that an admin that wants to give permission to a group has to first
disable all OTH bits in the file system.

Link: https://lkml.kernel.org/r/20210818153038.664127804@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 1261e8b41edb4281009a99b3c72d5b9ef50f7381..925a621b432e3c0c74e4fa329ad9689484bc9518 100644 (file)
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -432,7 +432,8 @@ static struct dentry *__create_dir(const char *name, struct dentry *parent,
        if (unlikely(!inode))
                return failed_creating(dentry);
 
-       inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+       /* Do not set bits for OTH */
+       inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
        inode->i_op = ops;
        inode->i_fop = &simple_dir_operations;