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>

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index a48aaa79d352313aa7dda46549f1a3d3e57b0c1f..6c1fb395bddfca86e3c00757a978ecfd85fef7c2 100644 (file)
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1675,8 +1675,16 @@ static struct random_ready_callback random_ready = {
 
 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) {