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From: Bernd Edlinger <bernd.edlinger@hotmail.de>
To: Theodore Ts'o <tytso@mit.edu>, Arnd Bergmann <arnd@arndb.de>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH] random: Make /dev/random wait for crng_ready
Date: Fri, 15 Feb 2019 01:47:16 +0000	[thread overview]
Message-ID: <VI1PR0702MB38408B595C818F1C3278873EE4600@VI1PR0702MB3840.eurprd07.prod.outlook.com> (raw)

Reading from /dev/random may return data while the getrandom
syscall is still blocking.

Those bytes are not yet cryptographically secure.

Make read and select for reading on /dev/random wait until
the crng is fully initialized.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
---
 drivers/char/random.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 38c6d1a..ddbc0e2 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -720,7 +720,7 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits)
 		}
 
 		/* should we wake readers? */
-		if (entropy_bits >= random_read_wakeup_bits &&
+		if (crng_ready() && entropy_bits >= random_read_wakeup_bits &&
 		    wq_has_sleeper(&random_read_wait)) {
 			wake_up_interruptible(&random_read_wait);
 			kill_fasync(&fasync, SIGIO, POLL_IN);
@@ -1851,7 +1851,9 @@ void rand_initialize_disk(struct gendisk *disk)
 
 	nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
 	while (1) {
-		n = extract_entropy_user(&blocking_pool, buf, nbytes);
+		n = crng_ready()
+			?  extract_entropy_user(&blocking_pool, buf, nbytes)
+			: 0;
 		if (n < 0)
 			return n;
 		trace_random_read(n*8, (nbytes-n)*8,
@@ -1865,6 +1867,7 @@ void rand_initialize_disk(struct gendisk *disk)
 			return -EAGAIN;
 
 		wait_event_interruptible(random_read_wait,
+			crng_ready() &&
 			ENTROPY_BITS(&input_pool) >=
 			random_read_wakeup_bits);
 		if (signal_pending(current))
@@ -1909,7 +1912,8 @@ void rand_initialize_disk(struct gendisk *disk)
 	poll_wait(file, &random_read_wait, wait);
 	poll_wait(file, &random_write_wait, wait);
 	mask = 0;
-	if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
+	if (crng_ready() &&
+		ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
 		mask |= EPOLLIN | EPOLLRDNORM;
 	if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
 		mask |= EPOLLOUT | EPOLLWRNORM;
-- 
1.9.1

             reply	other threads:[~2019-02-15  1:47 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-15  1:47 Bernd Edlinger [this message]
2019-02-15  5:40 ` [PATCH] random: Make /dev/random wait for crng_ready Bernd Edlinger
2019-02-15 13:58 ` [PATCHv2] " Bernd Edlinger
2019-02-16 18:23   ` Theodore Y. Ts'o
2019-02-16 20:12     ` Bernd Edlinger
2019-02-17  8:44     ` [PATCHv3] " Bernd Edlinger
2019-02-17 13:48       ` Bernd Edlinger
2019-02-17 20:55         ` [PATCHv4] random: Make /dev/random wait for input_pool initialized Bernd Edlinger
2019-02-19  7:16           ` Bernd Edlinger
2019-02-19 17:09             ` [PATCHv5] " Bernd Edlinger
2019-02-21  0:32               ` [PATCHv5] random: Make /dev/random wait for input_pool initializedy Theodore Y. Ts'o
2019-02-21 19:24                 ` Bernd Edlinger
2019-02-21 23:18                   ` Theodore Y. Ts'o
2019-02-22 13:45                     ` Bernd Edlinger

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