Fix some bugs in the /dev/random driver which causes getrandom(2) to

unblock earlier than designed.  Thanks to Jann Horn from Google's
 Project Zero for pointing this out to me.
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Merge tag 'random_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull /dev/random fixes from Ted Ts'o:
 "Fix some bugs in the /dev/random driver which causes getrandom(2) to
  unblock earlier than designed.

  Thanks to Jann Horn from Google's Project Zero for pointing this out
  to me"

* tag 'random_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: add new ioctl RNDRESEEDCRNG
  random: crng_reseed() should lock the crng instance that it is modifying
  random: set up the NUMA crng instances after the CRNG is fully initialized
  random: use a different mixing algorithm for add_device_randomness()
  random: fix crng_ready() test

drivers/char/random.c

@@ -427,8 +427,9 @@ struct crng_state primary_crng = {
  * its value (from 0->1->2).
  */
 static int crng_init = 0;
-#define crng_ready() (likely(crng_init > 0))
+#define crng_ready() (likely(crng_init > 1))
 static int crng_init_cnt = 0;
+static unsigned long crng_global_init_time = 0;
 #define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
 static void _extract_crng(struct crng_state *crng,
 			  __u32 out[CHACHA20_BLOCK_WORDS]);
@@ -787,6 +788,36 @@ static void crng_initialize(struct crng_state *crng)
 	crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
 }
 
+#ifdef CONFIG_NUMA
+static void numa_crng_init(void)
+{
+	int i;
+	struct crng_state *crng;
+	struct crng_state **pool;
+
+	pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
+	for_each_online_node(i) {
+		crng = kmalloc_node(sizeof(struct crng_state),
+				    GFP_KERNEL | __GFP_NOFAIL, i);
+		spin_lock_init(&crng->lock);
+		crng_initialize(crng);
+		pool[i] = crng;
+	}
+	mb();
+	if (cmpxchg(&crng_node_pool, NULL, pool)) {
+		for_each_node(i)
+			kfree(pool[i]);
+		kfree(pool);
+	}
+}
+#else
+static void numa_crng_init(void) {}
+#endif
+
+/*
+ * crng_fast_load() can be called by code in the interrupt service
+ * path.  So we can't afford to dilly-dally.
+ */
 static int crng_fast_load(const char *cp, size_t len)
 {
 	unsigned long flags;
@@ -794,7 +825,7 @@ static int crng_fast_load(const char *cp, size_t len)
 
 	if (!spin_trylock_irqsave(&primary_crng.lock, flags))
 		return 0;
-	if (crng_ready()) {
+	if (crng_init != 0) {
 		spin_unlock_irqrestore(&primary_crng.lock, flags);
 		return 0;
 	}
@@ -813,6 +844,51 @@ static int crng_fast_load(const char *cp, size_t len)
 	return 1;
 }
 
+/*
+ * crng_slow_load() is called by add_device_randomness, which has two
+ * attributes.  (1) We can't trust the buffer passed to it is
+ * guaranteed to be unpredictable (so it might not have any entropy at
+ * all), and (2) it doesn't have the performance constraints of
+ * crng_fast_load().
+ *
+ * So we do something more comprehensive which is guaranteed to touch
+ * all of the primary_crng's state, and which uses a LFSR with a
+ * period of 255 as part of the mixing algorithm.  Finally, we do
+ * *not* advance crng_init_cnt since buffer we may get may be something
+ * like a fixed DMI table (for example), which might very well be
+ * unique to the machine, but is otherwise unvarying.
+ */
+static int crng_slow_load(const char *cp, size_t len)
+{
+	unsigned long		flags;
+	static unsigned char	lfsr = 1;
+	unsigned char		tmp;
+	unsigned		i, max = CHACHA20_KEY_SIZE;
+	const char *		src_buf = cp;
+	char *			dest_buf = (char *) &primary_crng.state[4];
+
+	if (!spin_trylock_irqsave(&primary_crng.lock, flags))
+		return 0;
+	if (crng_init != 0) {
+		spin_unlock_irqrestore(&primary_crng.lock, flags);
+		return 0;
+	}
+	if (len > max)
+		max = len;
+
+	for (i = 0; i < max ; i++) {
+		tmp = lfsr;
+		lfsr >>= 1;
+		if (tmp & 1)
+			lfsr ^= 0xE1;
+		tmp = dest_buf[i % CHACHA20_KEY_SIZE];
+		dest_buf[i % CHACHA20_KEY_SIZE] ^= src_buf[i % len] ^ lfsr;
+		lfsr += (tmp << 3) | (tmp >> 5);
+	}
+	spin_unlock_irqrestore(&primary_crng.lock, flags);
+	return 1;
+}
+
 static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
 {
 	unsigned long	flags;
@@ -831,7 +907,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
 		_crng_backtrack_protect(&primary_crng, buf.block,
 					CHACHA20_KEY_SIZE);
 	}
-	spin_lock_irqsave(&primary_crng.lock, flags);
+	spin_lock_irqsave(&crng->lock, flags);
 	for (i = 0; i < 8; i++) {
 		unsigned long	rv;
 		if (!arch_get_random_seed_long(&rv) &&
@@ -841,9 +917,10 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
 	}
 	memzero_explicit(&buf, sizeof(buf));
 	crng->init_time = jiffies;
-	spin_unlock_irqrestore(&primary_crng.lock, flags);
+	spin_unlock_irqrestore(&crng->lock, flags);
 	if (crng == &primary_crng && crng_init < 2) {
 		invalidate_batched_entropy();
+		numa_crng_init();
 		crng_init = 2;
 		process_random_ready_list();
 		wake_up_interruptible(&crng_init_wait);
@@ -856,8 +933,9 @@ static void _extract_crng(struct crng_state *crng,
 {
 	unsigned long v, flags;
 
-	if (crng_init > 1 &&
+	if (crng_ready() &&
-	    time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL))
+	    (time_after(crng_global_init_time, crng->init_time) ||
+	     time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
 		crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
 	spin_lock_irqsave(&crng->lock, flags);
 	if (arch_get_random_long(&v))
@@ -981,10 +1059,8 @@ void add_device_randomness(const void *buf, unsigned int size)
 	unsigned long time = random_get_entropy() ^ jiffies;
 	unsigned long flags;
 
-	if (!crng_ready()) {
+	if (!crng_ready() && size)
-		crng_fast_load(buf, size);
+		crng_slow_load(buf, size);
-		return;
-	}
 
 	trace_add_device_randomness(size, _RET_IP_);
 	spin_lock_irqsave(&input_pool.lock, flags);
@@ -1139,7 +1215,7 @@ void add_interrupt_randomness(int irq, int irq_flags)
 	fast_mix(fast_pool);
 	add_interrupt_bench(cycles);
 
-	if (!crng_ready()) {
+	if (unlikely(crng_init == 0)) {
 		if ((fast_pool->count >= 64) &&
 		    crng_fast_load((char *) fast_pool->pool,
 				   sizeof(fast_pool->pool))) {
@@ -1680,28 +1756,10 @@ static void init_std_data(struct entropy_store *r)
  */
 static int rand_initialize(void)
 {
-#ifdef CONFIG_NUMA
-	int i;
-	struct crng_state *crng;
-	struct crng_state **pool;
-#endif
-
 	init_std_data(&input_pool);
 	init_std_data(&blocking_pool);
 	crng_initialize(&primary_crng);
-
+	crng_global_init_time = jiffies;
-#ifdef CONFIG_NUMA
-	pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
-	for_each_online_node(i) {
-		crng = kmalloc_node(sizeof(struct crng_state),
-				    GFP_KERNEL | __GFP_NOFAIL, i);
-		spin_lock_init(&crng->lock);
-		crng_initialize(crng);
-		pool[i] = crng;
-	}
-	mb();
-	crng_node_pool = pool;
-#endif
 	return 0;
 }
 early_initcall(rand_initialize);
@@ -1875,6 +1933,14 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 		input_pool.entropy_count = 0;
 		blocking_pool.entropy_count = 0;
 		return 0;
+	case RNDRESEEDCRNG:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		if (crng_init < 2)
+			return -ENODATA;
+		crng_reseed(&primary_crng, NULL);
+		crng_global_init_time = jiffies - 1;
+		return 0;
 	default:
 		return -EINVAL;
 	}
@@ -2212,7 +2278,7 @@ void add_hwgenerator_randomness(const char *buffer, size_t count,
 {
 	struct entropy_store *poolp = &input_pool;
 
-	if (!crng_ready()) {
+	if (unlikely(crng_init == 0)) {
 		crng_fast_load(buffer, count);
 		return;
 	}

include/uapi/linux/random.h

@@ -35,6 +35,9 @@
 /* Clear the entropy pool and associated counters.  (Superuser only.) */
 #define RNDCLEARPOOL	_IO( 'R', 0x06 )
 
+/* Reseed CRNG.  (Superuser only.) */
+#define RNDRESEEDCRNG	_IO( 'R', 0x07 )
+
 struct rand_pool_info {
 	int	entropy_count;
 	int	buf_size;