random: print a warning for the first ten uninitialized random users

Since systemd is consistently using /dev/urandom before it is
initialized, we can't see the other potentially dangerous users of
/dev/urandom immediately after boot.  So print the first ten such
complaints instead.

Cc: stable@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 8 insertions, 4 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 4e2627a8d226..d057438266bb 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1458,12 +1458,16 @@ 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)
 {
+        static int maxwarn = 10;
         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);
+        if (unlikely(nonblocking_pool.initialized == 0) &&
+            maxwarn > 0) {
+                maxwarn--;
+                printk(KERN_NOTICE "random: %s: uninitialized urandom read "
+                       "(%zd bytes read, %d bits of entropy available)\n",
+                       current->comm, nbytes, nonblocking_pool.entropy_total);
+        }
 
         nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
         ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);