From ffd80c5fc10ec6f31482dd42abc2e6aaa396fec0 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 12 May 2017 15:46:17 +0200
Subject: [PATCH] random: avoid preempt_disable()ed section

extract_crng() will use sleeping locks while in a preempt_disable()
section due to get_cpu_var().
Work around it with local_locks.

Cc: stable-rt@vger.kernel.org # where it applies to
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

diff --git a/drivers/char/random.c b/drivers/char/random.c
index f8794363e9c7..2267cebadf63 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -265,6 +265,7 @@
 #include <linux/syscalls.h>
 #include <linux/completion.h>
 #include <linux/uuid.h>
+#include <linux/locallock.h>
 #include <crypto/chacha20.h>
 
 #include <asm/processor.h>
@@ -2034,6 +2035,7 @@ static rwlock_t batched_entropy_reset_lock = __RW_LOCK_UNLOCKED(batched_entropy_
  * goal of being quite fast and not depleting entropy.
  */
 static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64);
+static DEFINE_LOCAL_IRQ_LOCK(batched_entropy_u64_lock);
 u64 get_random_u64(void)
 {
 	u64 ret;
@@ -2050,7 +2052,7 @@ u64 get_random_u64(void)
 	    return ret;
 #endif
 
-	batch = &get_cpu_var(batched_entropy_u64);
+	batch = &get_locked_var(batched_entropy_u64_lock, batched_entropy_u64);
 	if (use_lock)
 		read_lock_irqsave(&batched_entropy_reset_lock, flags);
 	if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
@@ -2060,12 +2062,13 @@ u64 get_random_u64(void)
 	ret = batch->entropy_u64[batch->position++];
 	if (use_lock)
 		read_unlock_irqrestore(&batched_entropy_reset_lock, flags);
-	put_cpu_var(batched_entropy_u64);
+	put_locked_var(batched_entropy_u64_lock, batched_entropy_u64);
 	return ret;
 }
 EXPORT_SYMBOL(get_random_u64);
 
 static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32);
+static DEFINE_LOCAL_IRQ_LOCK(batched_entropy_u32_lock);
 u32 get_random_u32(void)
 {
 	u32 ret;
@@ -2076,7 +2079,7 @@ u32 get_random_u32(void)
 	if (arch_get_random_int(&ret))
 		return ret;
 
-	batch = &get_cpu_var(batched_entropy_u32);
+	batch = &get_locked_var(batched_entropy_u32_lock, batched_entropy_u32);
 	if (use_lock)
 		read_lock_irqsave(&batched_entropy_reset_lock, flags);
 	if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
@@ -2086,7 +2089,7 @@ u32 get_random_u32(void)
 	ret = batch->entropy_u32[batch->position++];
 	if (use_lock)
 		read_unlock_irqrestore(&batched_entropy_reset_lock, flags);
-	put_cpu_var(batched_entropy_u32);
+	put_locked_var(batched_entropy_u32_lock, batched_entropy_u32);
 	return ret;
 }
 EXPORT_SYMBOL(get_random_u32);
-- 
2.1.4