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random: make /dev/random be almost like /dev/urandom

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This patch changes the read semantics of /dev/random to be the same
as /dev/urandom except that reads will block until the CRNG is
ready.

None of the cleanups that this enables have been done yet.  As a
result, this gives a warning about an unused function.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/5e6ac8831c6cf2e56a7a4b39616d1732b2bdd06c.1577088521.git.luto@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Andy Lutomirski 2019-12-23 00:20:48 -08:00 committed by Theodore Ts'o
parent 48446f198f
commit 30c08efec8
1 changed files with 14 additions and 41 deletions
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55
drivers/char/random.c
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@ -354,7 +354,6 @@
#define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
#define OUTPUT_POOL_SHIFT 10
#define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
#define SEC_XFER_SIZE 512
#define EXTRACT_SIZE 10
@ -803,7 +802,6 @@ retry:
if (entropy_bits >= random_read_wakeup_bits &&
wq_has_sleeper(&random_read_wait)) {
wake_up_interruptible(&random_read_wait);
kill_fasync(&fasync, SIGIO, POLL_IN);
}
/* If the input pool is getting full, and the blocking
* pool has room, send some entropy to the blocking
@ -1031,6 +1029,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
crng_init = 2;
process_random_ready_list();
wake_up_interruptible(&crng_init_wait);
kill_fasync(&fasync, SIGIO, POLL_IN);
pr_notice("random: crng init done\n");
if (unseeded_warning.missed) {
pr_notice("random: %d get_random_xx warning(s) missed "
@ -1982,43 +1981,6 @@ void rand_initialize_disk(struct gendisk *disk)
}
#endif
static ssize_t
_random_read(int nonblock, char __user *buf, size_t nbytes)
{
ssize_t n;
if (nbytes == 0)
return 0;
nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
while (1) {
n = extract_entropy_user(&blocking_pool, buf, nbytes);
if (n < 0)
return n;
trace_random_read(n*8, (nbytes-n)*8,
ENTROPY_BITS(&blocking_pool),
ENTROPY_BITS(&input_pool));
if (n > 0)
return n;
/* Pool is (near) empty. Maybe wait and retry. */
if (nonblock)
return -EAGAIN;
wait_event_interruptible(random_read_wait,
blocking_pool.initialized &&
(ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits));
if (signal_pending(current))
return -ERESTARTSYS;
}
}
static ssize_t
random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
}
static ssize_t
urandom_read_nowarn(struct file *file, char __user *buf, size_t nbytes,
loff_t *ppos)
@ -2051,15 +2013,26 @@ urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
return urandom_read_nowarn(file, buf, nbytes, ppos);
}
static ssize_t
random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
int ret;
ret = wait_for_random_bytes();
if (ret != 0)
return ret;
return urandom_read_nowarn(file, buf, nbytes, ppos);
}
static __poll_t
random_poll(struct file *file, poll_table * wait)
{
__poll_t mask;
poll_wait(file, &random_read_wait, wait);
poll_wait(file, &crng_init_wait, wait);
poll_wait(file, &random_write_wait, wait);
mask = 0;
if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
if (crng_ready())
mask |= EPOLLIN | EPOLLRDNORM;
if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
mask |= EPOLLOUT | EPOLLWRNORM;