random: Return nbytes filled from hw RNG

Currently the function get_random_bytes_arch() has return value 'void'.
If the hw RNG fails we currently fall back to using get_random_bytes().
This defeats the purpose of requesting random material from the hw RNG
in the first place.

There are currently no intree users of get_random_bytes_arch().

Only get random bytes from the hw RNG, make function return the number
of bytes retrieved from the hw RNG.

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

1 files changed, 9 insertions, 7 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 8e53e9515a1d..34ddfd57419b 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1725,26 +1725,28 @@ EXPORT_SYMBOL(del_random_ready_callback);
  * key known by the NSA).  So it's useful if we need the speed, but
  * only if we're willing to trust the hardware manufacturer not to
  * have put in a back door.
+ *
+ * Return number of bytes filled in.
  */
-void get_random_bytes_arch(void *buf, int nbytes)
+int __must_check get_random_bytes_arch(void *buf, int nbytes)
 {
+        int left = nbytes;
         char *p = buf;
 
-        trace_get_random_bytes_arch(nbytes, _RET_IP_);
-        while (nbytes) {
+        trace_get_random_bytes_arch(left, _RET_IP_);
+        while (left) {
                 unsigned long v;
-                int chunk = min(nbytes, (int)sizeof(unsigned long));
+                int chunk = min_t(int, left, sizeof(unsigned long));
 
                 if (!arch_get_random_long(&v))
                         break;
 
                 memcpy(p, &v, chunk);
                 p += chunk;
-                nbytes -= chunk;
+                left -= chunk;
         }
 
-        if (nbytes)
-                get_random_bytes(p, nbytes);
+        return nbytes - left;
 }
 EXPORT_SYMBOL(get_random_bytes_arch);