kprobes: Make list and blacklist root user read only

BugLink: https://bugs.launchpad.net/bugs/1792392

commit f2a3ab36 upstream.

Since the blacklist and list files on debugfs indicates
a sensitive address information to reader, it should be
restricted to the root user.
Suggested-by: Thomas Richter <tmricht@linux.ibm.com>
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Howells <dhowells@redhat.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Jon Medhurst <tixy@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tobin C . Harding <me@tobin.cc>
Cc: Will Deacon <will.deacon@arm.com>
Cc: acme@kernel.org
Cc: akpm@linux-foundation.org
Cc: brueckner@linux.vnet.ibm.com
Cc: linux-arch@vger.kernel.org
Cc: rostedt@goodmis.org
Cc: schwidefsky@de.ibm.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/lkml/152491890171.9916.5183693615601334087.stgit@devboxSigned-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

kernel/kprobes.c

@@ -2441,7 +2441,7 @@ static int __init debugfs_kprobe_init(void)
 	if (!dir)
 		return -ENOMEM;
 
-	file = debugfs_create_file("list", 0444, dir, NULL,
+	file = debugfs_create_file("list", 0400, dir, NULL,
 				&debugfs_kprobes_operations);
 	if (!file)
 		goto error;
@@ -2451,7 +2451,7 @@ static int __init debugfs_kprobe_init(void)
 	if (!file)
 		goto error;
 
-	file = debugfs_create_file("blacklist", 0444, dir, NULL,
+	file = debugfs_create_file("blacklist", 0400, dir, NULL,
 				&debugfs_kprobe_blacklist_ops);
 	if (!file)
 		goto error;