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

Date: Wed, 14 Jun 2017 21:29:16 +0200

Subject: Revert "random: invalidate batched entropy after crng init"

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

Git-commit: b0f2b48d4542c390ccc5e0f68b36e1c583ce8772

Patch-mainline: Queued in subsystem maintainer repository

References: SLE Realtime Extension

This reverts commit 86f95e53ed76fec2579e00351c6050ab398a7730.

In -RT lockdep complains with

| -> #1 (primary_crng.lock){+.+...}:

|        lock_acquire+0xb5/0x2b0

|        rt_spin_lock+0x46/0x50

|        _extract_crng+0x39/0xa0

|        extract_crng+0x3a/0x40

|        get_random_u64+0x17a/0x200

|        cache_random_seq_create+0x51/0x100

|        init_cache_random_seq+0x35/0x90

|        __kmem_cache_create+0xd3/0x560

|        create_boot_cache+0x8c/0xb2

|        create_kmalloc_cache+0x54/0x9f

|        create_kmalloc_caches+0xe3/0xfd

|        kmem_cache_init+0x14f/0x1f0

|        start_kernel+0x1e7/0x3b3

|        x86_64_start_reservations+0x2a/0x2c

|        x86_64_start_kernel+0x13d/0x14c

|        verify_cpu+0x0/0xfc

|

| -> #0 (batched_entropy_reset_lock){+.+...}:

|        __lock_acquire+0x11b4/0x1320

|        lock_acquire+0xb5/0x2b0

|        rt_write_lock+0x26/0x40

|        rt_write_lock_irqsave+0x9/0x10

|        invalidate_batched_entropy+0x28/0xb0

|        crng_fast_load+0xb5/0xe0

|        add_interrupt_randomness+0x16c/0x1a0

|        irq_thread+0x15c/0x1e0

|        kthread+0x112/0x150

|        ret_from_fork+0x31/0x40

so revert this for now and check later with upstream.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

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

---

 drivers/char/random.c |   37 -------------------------------------

 1 file changed, 37 deletions(-)

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

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

@@ -1,9 +1,6 @@

 /*

  * random.c -- A strong random number generator

  *

- * Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All

- * Rights Reserved.

- *

  * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005

  *

  * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.  All

@@ -780,8 +777,6 @@ static DECLARE_WAIT_QUEUE_HEAD(crng_init

 static struct crng_state **crng_node_pool __read_mostly;

 #endif

-static void invalidate_batched_entropy(void);

-

 static void crng_initialize(struct crng_state *crng)

 {

 	int		i;

@@ -864,7 +859,6 @@ static void crng_finalize_init(struct cr

 		return;

 	}

-	invalidate_batched_entropy();

 	numa_crng_init();

 	crng_init = 2;

 	process_random_ready_list();

@@ -904,7 +898,6 @@ static int crng_fast_load(const char *cp

 	}

 	spin_unlock_irqrestore(&primary_crng.lock, flags);

 	if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {

-		invalidate_batched_entropy();

 		crng_init = 1;

 		wake_up_interruptible(&crng_init_wait);

 		pr_notice("random: fast init done\n");

@@ -2189,7 +2182,6 @@ struct batched_entropy {

 	};

 	unsigned int position;

 };

-static rwlock_t batched_entropy_reset_lock = __RW_LOCK_UNLOCKED(batched_entropy_reset_lock);

 /*

  * Get a random word for internal kernel use only. The quality of the random

@@ -2203,20 +2195,14 @@ static DEFINE_PER_CPU(struct batched_ent

 u64 get_random_u64(void)

 {

 	u64 ret;

-	bool use_lock = READ_ONCE(crng_init) < 2;

-	unsigned long flags = 0;

 	struct batched_entropy *batch;

 	batch = &get_cpu_var(batched_entropy_u64);

-	if (use_lock)

-		read_lock_irqsave(&batched_entropy_reset_lock, flags);

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

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

 		batch->position = 0;

 	}

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

-	if (use_lock)

-		read_unlock_irqrestore(&batched_entropy_reset_lock, flags);

 	put_cpu_var(batched_entropy_u64);

 	return ret;

 }

@@ -2226,42 +2212,19 @@ static DEFINE_PER_CPU(struct batched_ent

 u32 get_random_u32(void)

 {

 	u32 ret;

-	bool use_lock = READ_ONCE(crng_init) < 2;

-	unsigned long flags = 0;

 	struct batched_entropy *batch;

 	batch = &get_cpu_var(batched_entropy_u32);

-	if (use_lock)

-		read_lock_irqsave(&batched_entropy_reset_lock, flags);

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

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

 		batch->position = 0;

 	}

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

-	if (use_lock)

-		read_unlock_irqrestore(&batched_entropy_reset_lock, flags);

 	put_cpu_var(batched_entropy_u32);

 	return ret;

 }

 EXPORT_SYMBOL(get_random_u32);

-/* It's important to invalidate all potential batched entropy that might

- * be stored before the crng is initialized, which we can do lazily by

- * simply resetting the counter to zero so that it's re-extracted on the

- * next usage. */

-static void invalidate_batched_entropy(void)

-{

-	int cpu;

-	unsigned long flags;

-

-	write_lock_irqsave(&batched_entropy_reset_lock, flags);

-	for_each_possible_cpu (cpu) {

-		per_cpu_ptr(&batched_entropy_u32, cpu)->position = 0;

-		per_cpu_ptr(&batched_entropy_u64, cpu)->position = 0;

-	}

-	write_unlock_irqrestore(&batched_entropy_reset_lock, flags);

-}

-

 /**

  * randomize_page - Generate a random, page aligned address

  * @start:	The smallest acceptable address the caller will take.