Re: [PATCH 3/5] random: set up the NUMA crng instances after the CRNG is fully initialized

[kbuild test robot]

Hi Theodore,

I love your patch! Perhaps something to improve:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on v4.16 next-20180413]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]

url:
https://github.com/0day-ci/linux/commits/Theodore-Ts-o/random-fix-crng_ready-test/20180414-055120
config: i386-randconfig-x014-201814 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
# save the attached .config to linux build tree
make ARCH=i386 

All warnings (new ones prefixed by >>):

   drivers/char/random.c: In function 'numa_crng_init':
>> drivers/char/random.c:813:1: warning: no return statement in function 
>> returning non-void [-Wreturn-type]
static int numa_crng_init(void) {}
^~

vim +813 drivers/char/random.c

   789  
   790  #ifdef CONFIG_NUMA
   791  static void numa_crng_init(void)
   792  {
   793  int i;
   794  struct crng_state *crng;
   795  struct crng_state **pool;
   796  
   797  pool = kcalloc(nr_node_ids, sizeof(*pool), 
GFP_KERNEL|__GFP_NOFAIL);
   798  for_each_online_node(i) {
   799  crng = kmalloc_node(sizeof(struct crng_state),
   800  GFP_KERNEL | __GFP_NOFAIL, i);
   801  spin_lock_init(&crng->lock);
   802  crng_initialize(crng);
   803  pool[i] = crng;
   804  }
   805  mb();
   806  if (cmpxchg(&crng_node_pool, NULL, pool)) {
   807  for_each_node(i)
   808  kfree(pool[i]);
   809  kfree(pool);
   810  }
   811  }
   812  #else
 > 813  static int numa_crng_init(void) {}
   814  #endif
   815  

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation


.config.gz
Description: application/gzip

[PATCH 3/5] random: set up the NUMA crng instances after the CRNG is fully initialized

[Theodore Ts'o]

Until the primary_crng is fully initialized, don't initialize the NUMA
crng nodes.  Otherwise users of /dev/urandom on NUMA systems before
the CRNG is fully initialized can get very bad quality randomness.  Of
course everyone should move to getrandom(2) where this won't be an
issue, but there's a lot of legacy code out there.

Reported-by: Jann Horn 
Fixes: 1e7f583af67b ("random: make /dev/urandom scalable for silly...")
Cc: sta...@kernel.org # 4.8+
Signed-off-by: Theodore Ts'o 
---
 drivers/char/random.c | 46 +++---
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 2154a5fe4c81..681ee0c0de24 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -787,6 +787,32 @@ static void crng_initialize(struct crng_state *crng)
crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
 }
 
+#ifdef CONFIG_NUMA
+static void numa_crng_init(void)
+{
+   int i;
+   struct crng_state *crng;
+   struct crng_state **pool;
+
+   pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
+   for_each_online_node(i) {
+   crng = kmalloc_node(sizeof(struct crng_state),
+   GFP_KERNEL | __GFP_NOFAIL, i);
+   spin_lock_init(&crng->lock);
+   crng_initialize(crng);
+   pool[i] = crng;
+   }
+   mb();
+   if (cmpxchg(&crng_node_pool, NULL, pool)) {
+   for_each_node(i)
+   kfree(pool[i]);
+   kfree(pool);
+   }
+}
+#else
+static int numa_crng_init(void) {}
+#endif
+
 /*
  * crng_fast_load() can be called by code in the interrupt service
  * path.  So we can't afford to dilly-dally.
@@ -893,6 +919,7 @@ static void crng_reseed(struct crng_state *crng, struct 
entropy_store *r)
spin_unlock_irqrestore(&primary_crng.lock, flags);
if (crng == &primary_crng && crng_init < 2) {
invalidate_batched_entropy();
+   numa_crng_init();
crng_init = 2;
process_random_ready_list();
wake_up_interruptible(&crng_init_wait);
@@ -1727,28 +1754,9 @@ static void init_std_data(struct entropy_store *r)
  */
 static int rand_initialize(void)
 {
-#ifdef CONFIG_NUMA
-   int i;
-   struct crng_state *crng;
-   struct crng_state **pool;
-#endif
-
init_std_data(&input_pool);
init_std_data(&blocking_pool);
crng_initialize(&primary_crng);
-
-#ifdef CONFIG_NUMA
-   pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
-   for_each_online_node(i) {
-   crng = kmalloc_node(sizeof(struct crng_state),
-   GFP_KERNEL | __GFP_NOFAIL, i);
-   spin_lock_init(&crng->lock);
-   crng_initialize(crng);
-   pool[i] = crng;
-   }
-   mb();
-   crng_node_pool = pool;
-#endif
return 0;
 }
 early_initcall(rand_initialize);
-- 
2.16.1.72.g5be1f00a9a