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.edlin...@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
