[PATCH] random: fix possible sleeping allocation from irq context

[Theodore Ts'o <tytso@mit.edu>]

We can do a sleeping allocation from an irq context when CONFIG_NUMA
is enabled.  Fix this by initializing the NUMA crng instances in a
workqueue.

Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot+9de458f6a5e713ee8c1a@syzkaller.appspotmail.com
Fixes: 8ef35c866f8862df ("random: set up the NUMA crng instances...")
Cc: stable@vger.kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
 drivers/char/random.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 3cd3aae24d6d..e182cca7e6cd 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -789,7 +789,7 @@ static void crng_initialize(struct crng_state *crng)
 }
 
 #ifdef CONFIG_NUMA
-static void numa_crng_init(void)
+static void do_numa_crng_init(struct work_struct *work)
 {
 	int i;
 	struct crng_state *crng;
@@ -810,6 +810,13 @@ static void numa_crng_init(void)
 		kfree(pool);
 	}
 }
+
+DECLARE_WORK(numa_crng_init_work, do_numa_crng_init);
+
+static void numa_crng_init(void)
+{
+	schedule_work(&numa_crng_init_work);
+}
 #else
 static void numa_crng_init(void) {}
 #endif
-- 
2.16.1.72.g5be1f00a9a