random: printk notifications for urandom pool initialization

Print a notification to the console when the nonblocking pool is
initialized.  Also printk a warning when a process tries reading from
/dev/urandom before it is fully initialized.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 11 insertions, 1 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 62923138e77a..a19a7a63ec35 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -655,6 +655,9 @@ retry:
         r->entropy_total += nbits;
         if (!r->initialized && nbits > 0) {
                 if (r->entropy_total > 128) {
+                        if (r == &nonblocking_pool)
+                                pr_notice("random: %s pool is initialized\n",
+                                          r->name);
                         r->initialized = 1;
                         r->entropy_total = 0;
                 }
@@ -1327,7 +1330,14 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 static ssize_t
 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 {
-        int ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
+        int ret;
+
+        if (unlikely(nonblocking_pool.initialized == 0))
+                printk_once(KERN_NOTICE "random: %s urandom read "
+                            "with %d bits of entropy available\n",
+                            current->comm, nonblocking_pool.entropy_total);
+
+        ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
 
         trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
                            ENTROPY_BITS(&input_pool));