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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 12 May 2017 15:46:17 +0200
Subject: [PATCH] random: avoid preempt_disable()ed section
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.13-rt10.tar.xz
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>
---
drivers/char/random.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
--- 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>
@@ -2223,6 +2224,7 @@ static rwlock_t batched_entropy_reset_lo
* at any 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;
@@ -2243,7 +2245,7 @@ u64 get_random_u64(void)
warn_unseeded_randomness(&previous);
use_lock = READ_ONCE(crng_init) < 2;
- 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) {
@@ -2253,12 +2255,13 @@ 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;
@@ -2273,7 +2276,7 @@ u32 get_random_u32(void)
warn_unseeded_randomness(&previous);
use_lock = READ_ONCE(crng_init) < 2;
- 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) {
@@ -2283,7 +2286,7 @@ 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);
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