Message-Id: <20220211123546.474952-5-Jason@zx2c4.com>
Date:   Fri, 11 Feb 2022 13:35:41 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-kernel@...r.kernel.org, linux@...inikbrodowski.net
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>
Subject: [PATCH 4/9] random: group initialization wait functions

This pulls all of the readiness waiting-focused functions into the first
labeled section.

No functional changes.

Cc: Theodore Ts'o <tytso@....edu>
Cc: Dominik Brodowski <linux@...inikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 drivers/char/random.c | 334 ++++++++++++++++++++++--------------------
 1 file changed, 174 insertions(+), 160 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 149cbd481b96..09a85a1a4458 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -59,44 +59,200 @@
 #include <asm/irq_regs.h>
 #include <asm/io.h>
 
-enum {
-	POOL_BITS = BLAKE2S_HASH_SIZE * 8,
-	POOL_MIN_BITS = POOL_BITS /* No point in settling for less. */
-};
 
-/*
- * Static global variables
- */
-static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
-static struct fasync_struct *fasync;
-
-static DEFINE_SPINLOCK(random_ready_list_lock);
-static LIST_HEAD(random_ready_list);
+/*********************************************************************
+ *
+ * Initialization and readiness waiting.
+ *
+ * Much of the RNG infrastructure is devoted to various dependencies
+ * being able to wait until the RNG has collected enough entropy and
+ * is ready for safe consumption.
+ *
+ *********************************************************************/
 
 /*
  * crng_init =  0 --> Uninitialized
  *		1 --> Initialized
  *		2 --> Initialized from input_pool
  *
- * crng_init is protected by primary_crng->lock, and only increases
+ * crng_init is protected by base_crng->lock, and only increases
  * its value (from 0->1->2).
  */
 static int crng_init = 0;
 #define crng_ready() (likely(crng_init > 1))
-static int crng_init_cnt = 0;
-static void process_random_ready_list(void);
-static void _get_random_bytes(void *buf, size_t nbytes);
+/* Various types of waiters for crng_init->2 transition. */
+static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
+static struct fasync_struct *fasync;
+static DEFINE_SPINLOCK(random_ready_list_lock);
+static LIST_HEAD(random_ready_list);
 
+/* Control how we warn userspace. */
 static struct ratelimit_state unseeded_warning =
 	RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
 static struct ratelimit_state urandom_warning =
 	RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
-
 static int ratelimit_disable __read_mostly;
-
 module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
 MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
 
+/*
+ * Returns whether or not the urandom pool has been seeded and thus guaranteed
+ * to supply cryptographically secure random numbers. This applies to: the
+ * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
+ * ,u64,int,long} family of functions.
+ *
+ * Returns: true if the urandom pool has been seeded.
+ *          false if the urandom pool has not been seeded.
+ */
+bool rng_is_initialized(void)
+{
+	return crng_ready();
+}
+EXPORT_SYMBOL(rng_is_initialized);
+
+/* Used by wait_for_random_bytes(), and considered an entropy collector, below. */
+static void try_to_generate_entropy(void);
+
+/*
+ * Wait for the urandom pool to be seeded and thus guaranteed to supply
+ * cryptographically secure random numbers. This applies to: the /dev/urandom
+ * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
+ * family of functions. Using any of these functions without first calling
+ * this function forfeits the guarantee of security.
+ *
+ * Returns: 0 if the urandom pool has been seeded.
+ *          -ERESTARTSYS if the function was interrupted by a signal.
+ */
+int wait_for_random_bytes(void)
+{
+	if (likely(crng_ready()))
+		return 0;
+
+	do {
+		int ret;
+		ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
+		if (ret)
+			return ret > 0 ? 0 : ret;
+
+		try_to_generate_entropy();
+	} while (!crng_ready());
+
+	return 0;
+}
+EXPORT_SYMBOL(wait_for_random_bytes);
+
+/*
+ * Add a callback function that will be invoked when the nonblocking
+ * pool is initialised.
+ *
+ * returns: 0 if callback is successfully added
+ *	    -EALREADY if pool is already initialised (callback not called)
+ *	    -ENOENT if module for callback is not alive
+ */
+int add_random_ready_callback(struct random_ready_callback *rdy)
+{
+	struct module *owner;
+	unsigned long flags;
+	int err = -EALREADY;
+
+	if (crng_ready())
+		return err;
+
+	owner = rdy->owner;
+	if (!try_module_get(owner))
+		return -ENOENT;
+
+	spin_lock_irqsave(&random_ready_list_lock, flags);
+	if (crng_ready())
+		goto out;
+
+	owner = NULL;
+
+	list_add(&rdy->list, &random_ready_list);
+	err = 0;
+
+out:
+	spin_unlock_irqrestore(&random_ready_list_lock, flags);
+
+	module_put(owner);
+
+	return err;
+}
+EXPORT_SYMBOL(add_random_ready_callback);
+
+/*
+ * Delete a previously registered readiness callback function.
+ */
+void del_random_ready_callback(struct random_ready_callback *rdy)
+{
+	unsigned long flags;
+	struct module *owner = NULL;
+
+	spin_lock_irqsave(&random_ready_list_lock, flags);
+	if (!list_empty(&rdy->list)) {
+		list_del_init(&rdy->list);
+		owner = rdy->owner;
+	}
+	spin_unlock_irqrestore(&random_ready_list_lock, flags);
+
+	module_put(owner);
+}
+EXPORT_SYMBOL(del_random_ready_callback);
+
+static void process_random_ready_list(void)
+{
+	unsigned long flags;
+	struct random_ready_callback *rdy, *tmp;
+
+	spin_lock_irqsave(&random_ready_list_lock, flags);
+	list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
+		struct module *owner = rdy->owner;
+
+		list_del_init(&rdy->list);
+		rdy->func(rdy);
+		module_put(owner);
+	}
+	spin_unlock_irqrestore(&random_ready_list_lock, flags);
+}
+
+#define warn_unseeded_randomness(previous) \
+	_warn_unseeded_randomness(__func__, (void *)_RET_IP_, (previous))
+
+static void _warn_unseeded_randomness(const char *func_name, void *caller, void **previous)
+{
+#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
+	const bool print_once = false;
+#else
+	static bool print_once __read_mostly;
+#endif
+
+	if (print_once || crng_ready() ||
+	    (previous && (caller == READ_ONCE(*previous))))
+		return;
+	WRITE_ONCE(*previous, caller);
+#ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
+	print_once = true;
+#endif
+	if (__ratelimit(&unseeded_warning))
+		printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n",
+				func_name, caller, crng_init);
+}
+
+
+enum {
+	POOL_BITS = BLAKE2S_HASH_SIZE * 8,
+	POOL_MIN_BITS = POOL_BITS /* No point in settling for less. */
+};
+
+/*
+ * Static global variables
+ */
+static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
+static struct fasync_struct *fasync;
+
+static int crng_init_cnt = 0;
+static void _get_random_bytes(void *buf, size_t nbytes);
+
 /**********************************************************************
  *
  * OS independent entropy store.   Here are the functions which handle
@@ -177,22 +333,6 @@ static void fast_mix(u32 pool[4])
 	pool[2] = c;  pool[3] = d;
 }
 
-static void process_random_ready_list(void)
-{
-	unsigned long flags;
-	struct random_ready_callback *rdy, *tmp;
-
-	spin_lock_irqsave(&random_ready_list_lock, flags);
-	list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
-		struct module *owner = rdy->owner;
-
-		list_del_init(&rdy->list);
-		rdy->func(rdy);
-		module_put(owner);
-	}
-	spin_unlock_irqrestore(&random_ready_list_lock, flags);
-}
-
 static void credit_entropy_bits(size_t nbits)
 {
 	unsigned int entropy_count, orig, add;
@@ -242,8 +382,6 @@ static DEFINE_PER_CPU(struct crng, crngs) = {
 	.lock = INIT_LOCAL_LOCK(crngs.lock),
 };
 
-static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
-
 /*
  * crng_fast_load() can be called by code in the interrupt service
  * path.  So we can't afford to dilly-dally. Returns the number of
@@ -761,29 +899,6 @@ static bool drain_entropy(void *buf, size_t nbytes)
 	return true;
 }
 
-#define warn_unseeded_randomness(previous) \
-	_warn_unseeded_randomness(__func__, (void *)_RET_IP_, (previous))
-
-static void _warn_unseeded_randomness(const char *func_name, void *caller, void **previous)
-{
-#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
-	const bool print_once = false;
-#else
-	static bool print_once __read_mostly;
-#endif
-
-	if (print_once || crng_ready() ||
-	    (previous && (caller == READ_ONCE(*previous))))
-		return;
-	WRITE_ONCE(*previous, caller);
-#ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
-	print_once = true;
-#endif
-	if (__ratelimit(&unseeded_warning))
-		printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n",
-				func_name, caller, crng_init);
-}
-
 /*
  * This function is the exported kernel interface.  It returns some
  * number of good random numbers, suitable for key generation, seeding
@@ -885,107 +1000,6 @@ static void try_to_generate_entropy(void)
 	mix_pool_bytes(&stack.now, sizeof(stack.now));
 }
 
-/*
- * Wait for the urandom pool to be seeded and thus guaranteed to supply
- * cryptographically secure random numbers. This applies to: the /dev/urandom
- * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
- * family of functions. Using any of these functions without first calling
- * this function forfeits the guarantee of security.
- *
- * Returns: 0 if the urandom pool has been seeded.
- *          -ERESTARTSYS if the function was interrupted by a signal.
- */
-int wait_for_random_bytes(void)
-{
-	if (likely(crng_ready()))
-		return 0;
-
-	do {
-		int ret;
-		ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
-		if (ret)
-			return ret > 0 ? 0 : ret;
-
-		try_to_generate_entropy();
-	} while (!crng_ready());
-
-	return 0;
-}
-EXPORT_SYMBOL(wait_for_random_bytes);
-
-/*
- * Returns whether or not the urandom pool has been seeded and thus guaranteed
- * to supply cryptographically secure random numbers. This applies to: the
- * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
- * ,u64,int,long} family of functions.
- *
- * Returns: true if the urandom pool has been seeded.
- *          false if the urandom pool has not been seeded.
- */
-bool rng_is_initialized(void)
-{
-	return crng_ready();
-}
-EXPORT_SYMBOL(rng_is_initialized);
-
-/*
- * Add a callback function that will be invoked when the nonblocking
- * pool is initialised.
- *
- * returns: 0 if callback is successfully added
- *	    -EALREADY if pool is already initialised (callback not called)
- *	    -ENOENT if module for callback is not alive
- */
-int add_random_ready_callback(struct random_ready_callback *rdy)
-{
-	struct module *owner;
-	unsigned long flags;
-	int err = -EALREADY;
-
-	if (crng_ready())
-		return err;
-
-	owner = rdy->owner;
-	if (!try_module_get(owner))
-		return -ENOENT;
-
-	spin_lock_irqsave(&random_ready_list_lock, flags);
-	if (crng_ready())
-		goto out;
-
-	owner = NULL;
-
-	list_add(&rdy->list, &random_ready_list);
-	err = 0;
-
-out:
-	spin_unlock_irqrestore(&random_ready_list_lock, flags);
-
-	module_put(owner);
-
-	return err;
-}
-EXPORT_SYMBOL(add_random_ready_callback);
-
-/*
- * Delete a previously registered readiness callback function.
- */
-void del_random_ready_callback(struct random_ready_callback *rdy)
-{
-	unsigned long flags;
-	struct module *owner = NULL;
-
-	spin_lock_irqsave(&random_ready_list_lock, flags);
-	if (!list_empty(&rdy->list)) {
-		list_del_init(&rdy->list);
-		owner = rdy->owner;
-	}
-	spin_unlock_irqrestore(&random_ready_list_lock, flags);
-
-	module_put(owner);
-}
-EXPORT_SYMBOL(del_random_ready_callback);
-
 /*
  * This function will use the architecture-specific hardware random
  * number generator if it is available. It is not recommended for
-- 
2.35.0

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