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Subject[PATCH RT 3/8] random: avoid preempt_disable()ed section
4.4.97-rt111-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

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

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: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
drivers/char/random.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index fecc40a69df8..b41745c5962c 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -260,6 +260,7 @@
#include <linux/irq.h>
#include <linux/syscalls.h>
#include <linux/completion.h>
+#include <linux/locallock.h>

#include <asm/processor.h>
#include <asm/uaccess.h>
@@ -1796,6 +1797,7 @@ int random_int_secret_init(void)

static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash)
__aligned(sizeof(unsigned long));
+static DEFINE_LOCAL_IRQ_LOCK(hash_entropy_int_lock);

/*
* Get a random word for internal kernel use only. Similar to urandom but
@@ -1811,12 +1813,12 @@ unsigned int get_random_int(void)
if (arch_get_random_int(&ret))
return ret;

- hash = get_cpu_var(get_random_int_hash);
+ hash = &get_locked_var(hash_entropy_int_lock, get_random_int_hash);

hash[0] += current->pid + jiffies + random_get_entropy();
md5_transform(hash, random_int_secret);
ret = hash[0];
- put_cpu_var(get_random_int_hash);
+ put_locked_var(hash_entropy_int_lock, get_random_int_hash);

return ret;
}
@@ -1833,12 +1835,12 @@ unsigned long get_random_long(void)
if (arch_get_random_long(&ret))
return ret;

- hash = get_cpu_var(get_random_int_hash);
+ hash = &get_locked_var(hash_entropy_int_lock, get_random_int_hash);

hash[0] += current->pid + jiffies + random_get_entropy();
md5_transform(hash, random_int_secret);
ret = *(unsigned long *)hash;
- put_cpu_var(get_random_int_hash);
+ put_locked_var(hash_entropy_int_lock, get_random_int_hash);

return ret;
}
--
2.13.2

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