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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Theodore Tso <tytso@mit.edu>,
        stable@kernel.org
Subject: [PATCH 4.9 77/95] random: add new ioctl RNDRESEEDCRNG
Date:   Sun, 22 Apr 2018 15:53:46 +0200
Message-Id: <20180422135213.580990477@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Theodore Ts'o <tytso@mit.edu>

commit d848e5f8e1ebdb227d045db55fe4f825e82965fa upstream.

Add a new ioctl which forces the the crng to be reseeded.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/char/random.c       |   13 ++++++++++++-
 include/uapi/linux/random.h |    3 +++
 2 files changed, 15 insertions(+), 1 deletion(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -436,6 +436,7 @@ struct crng_state primary_crng = {
 static int 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,
 			  __u8 out[CHACHA20_BLOCK_SIZE]);
@@ -900,7 +901,8 @@ static void _extract_crng(struct crng_st
 	unsigned long v, flags;
 
 	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))
@@ -1689,6 +1691,7 @@ static int rand_initialize(void)
 	init_std_data(&input_pool);
 	init_std_data(&blocking_pool);
 	crng_initialize(&primary_crng);
+	crng_global_init_time = jiffies;
 	return 0;
 }
 early_initcall(rand_initialize);
@@ -1862,6 +1865,14 @@ static long random_ioctl(struct file *f,
 		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;
 	}
--- a/include/uapi/linux/random.h
+++ b/include/uapi/linux/random.h
@@ -34,6 +34,9 @@
 /* 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;