From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Date: Fri, 12 May 2017 15:46:17 +0200

Subject: random: avoid preempt_disable()ed section

Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git

Git-commit: 4bed11300e24d5178829758e535cc4996490b7c8

Patch-mainline: Queued in subsystem maintainer repository

References: SLE Realtime Extension

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>

Signed-off-by: Mike Galbraith <mgalbraith@suse.de>

---

 drivers/char/random.c |   11 +++++++----

 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/char/random.c

+++ b/drivers/char/random.c

@@ -263,6 +263,7 @@

 #include <linux/syscalls.h>

 #include <linux/completion.h>

 #include <linux/uuid.h>

+#include <linux/locallock.h>

 #include <crypto/chacha20.h>

 #include <asm/processor.h>

@@ -2191,35 +2192,37 @@ struct batched_entropy {

  * point prior.

  */

 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;

 	struct batched_entropy *batch;

-	batch = &get_cpu_var(batched_entropy_u64);

+	batch = &get_locked_var(batched_entropy_u64_lock, batched_entropy_u64);

 	if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {

 		extract_crng((u8 *)batch->entropy_u64);

 		batch->position = 0;

 	}

 	ret = batch->entropy_u64[batch->position++];

-	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;

 	struct batched_entropy *batch;

-	batch = &get_cpu_var(batched_entropy_u32);

+	batch = &get_locked_var(batched_entropy_u32_lock, batched_entropy_u32);

 	if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {

 		extract_crng((u8 *)batch->entropy_u32);

 		batch->position = 0;

 	}

 	ret = batch->entropy_u32[batch->position++];

-	put_cpu_var(batched_entropy_u32);

+	put_locked_var(batched_entropy_u32_lock, batched_entropy_u32);

 	return ret;

 }

 EXPORT_SYMBOL(get_random_u32);