random: rate limit unseeded randomness warnings

BugLink: http://bugs.launchpad.net/bugs/1778265
commit 4e00b339e264802851aff8e73cde7d24b57b18ce upstream.

On systems without sufficient boot randomness, no point spamming dmesg.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/char/random.c b/drivers/char/random.c
index b57296d54ead3789efff7e0afcb2917ec3b5b080..be2aba73deda3c6df97b53144b01ef11c6f26ede 100644 (file)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -261,6 +261,7 @@
 #include <linux/ptrace.h>
 #include <linux/workqueue.h>
 #include <linux/irq.h>
+#include <linux/ratelimit.h>
 #include <linux/syscalls.h>
 #include <linux/completion.h>
 #include <linux/uuid.h>
@@ -438,6 +439,16 @@ static void _crng_backtrack_protect(struct crng_state *crng,
 static void process_random_ready_list(void);
 static void _get_random_bytes(void *buf, int nbytes);
 
+static struct ratelimit_state unseeded_warning =
+       RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
+static struct ratelimit_state urandom_warning =
+       RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
+
+static int ratelimit_disable __read_mostly;
+
+module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
+MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
+
 /**********************************************************************
  *
  * OS independent entropy store.   Here are the functions which handle
@@ -931,6 +942,18 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
                process_random_ready_list();
                wake_up_interruptible(&crng_init_wait);
                pr_notice("random: crng init done\n");
+               if (unseeded_warning.missed) {
+                       pr_notice("random: %d get_random_xx warning(s) missed "
+                                 "due to ratelimiting\n",
+                                 unseeded_warning.missed);
+                       unseeded_warning.missed = 0;
+               }
+               if (urandom_warning.missed) {
+                       pr_notice("random: %d urandom warning(s) missed "
+                                 "due to ratelimiting\n",
+                                 urandom_warning.missed);
+                       urandom_warning.missed = 0;
+               }
        }
 }
 
@@ -1574,8 +1597,9 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller,
 #ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
        print_once = true;
 #endif
-       pr_notice("random: %s called from %pS with crng_init=%d\n",
-                 func_name, caller, crng_init);
+       if (__ratelimit(&unseeded_warning))
+               pr_notice("random: %s called from %pS with crng_init=%d\n",
+                         func_name, caller, crng_init);
 }
 
 /*
@@ -1769,6 +1793,10 @@ static int rand_initialize(void)
        init_std_data(&blocking_pool);
        crng_initialize(&primary_crng);
        crng_global_init_time = jiffies;
+       if (ratelimit_disable) {
+               urandom_warning.interval = 0;
+               unseeded_warning.interval = 0;
+       }
        return 0;
 }
 early_initcall(rand_initialize);
@@ -1836,9 +1864,10 @@ urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 
        if (!crng_ready() && maxwarn > 0) {
                maxwarn--;
-               printk(KERN_NOTICE "random: %s: uninitialized urandom read "
-                      "(%zd bytes read)\n",
-                      current->comm, nbytes);
+               if (__ratelimit(&urandom_warning))
+                       printk(KERN_NOTICE "random: %s: uninitialized "
+                              "urandom read (%zd bytes read)\n",
+                              current->comm, nbytes);
                spin_lock_irqsave(&primary_crng.lock, flags);
                crng_init_cnt = 0;
                spin_unlock_irqrestore(&primary_crng.lock, flags);