commit 1c4facb846c7f863bc65483394e80acdbacf671b
author Tobin C. Harding <me@tobin.cc> Fri Jun 22 09:15:33 2018 +1000
committer Theodore Ts'o <tytso@mit.edu> Tue Jul 17 21:32:48 2018 -0400
tree 4c43ef97d6ecf95df31b4be6c08178b3fa204914
parent 753d433b586d1d43c487e3d660f5778c7c8d58ea

vsprintf: Use hw RNG for ptr_key

Currently we must wait for enough entropy to become available before
hashed pointers can be printed.  We can remove this wait by using the
hw RNG if available.

Use hw RNG to get keying material.

Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

lib/vsprintf.c

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index a48aaa7..6c1fb39 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1675,8 +1675,16 @@
 
 static int __init initialize_ptr_random(void)
 {
-	int ret = add_random_ready_callback(&random_ready);
+	int key_size = sizeof(ptr_key);
+	int ret;
 
+	/* Use hw RNG if available. */
+	if (get_random_bytes_arch(&ptr_key, key_size) == key_size) {
+		static_branch_disable(&not_filled_random_ptr_key);
+		return 0;
+	}
+
+	ret = add_random_ready_callback(&random_ready);
 	if (!ret) {
 		return 0;
 	} else if (ret == -EALREADY) {