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Commit 43e62db8 authored by Jens Axboe's avatar Jens Axboe Committed by Greg Kroah-Hartman
Browse files

random: convert to using fops->read_iter() 



commit 1b388e7765f2eaa137cf5d92b47ef5925ad83ced upstream.

This is a pre-requisite to wiring up splice() again for the random
and urandom drivers. It also allows us to remove the INT_MAX check in
getrandom(), because import_single_range() applies capping internally.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
[Jason: rewrote get_random_bytes_user() to simplify and also incorporate
 additional suggestions from Al.]
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c23188fa

drivers/char/random.c

+30 −36
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ 
#include <linux/uuid.h>

#include <linux/uaccess.h>

#include <linux/siphash.h>

#include <linux/uio.h>

#include <crypto/chacha.h>

#include <crypto/blake2s.h>

#include <asm/processor.h>
@@ -446,13 +447,13 @@ void get_random_bytes(void *buf, size_t len) 
}

EXPORT_SYMBOL(get_random_bytes);



static ssize_t get_random_bytes_user(void __user *ubuf, size_t len)

static ssize_t get_random_bytes_user(struct iov_iter *iter)

{

	size_t block_len, left, ret = 0;

	u32 chacha_state[CHACHA_BLOCK_SIZE / sizeof(u32)];

	u8 output[CHACHA_BLOCK_SIZE];

	u8 block[CHACHA_BLOCK_SIZE];

	size_t ret = 0, copied;



	if (!len)

	if (unlikely(!iov_iter_count(iter)))

		return 0;



	/*
@@ -466,30 +467,22 @@ static ssize_t get_random_bytes_user(void __user *ubuf, size_t len) 
	 * use chacha_state after, so we can simply return those bytes to

	 * the user directly.

	 */

	if (len <= CHACHA_KEY_SIZE) {

		ret = len - copy_to_user(ubuf, &chacha_state[4], len);

	if (iov_iter_count(iter) <= CHACHA_KEY_SIZE) {

		ret = copy_to_iter(&chacha_state[4], CHACHA_KEY_SIZE, iter);

		goto out_zero_chacha;

	}



	for (;;) {

		chacha20_block(chacha_state, output);

		chacha20_block(chacha_state, block);

		if (unlikely(chacha_state[12] == 0))

			++chacha_state[13];



		block_len = min_t(size_t, len, CHACHA_BLOCK_SIZE);

		left = copy_to_user(ubuf, output, block_len);

		if (left) {

			ret += block_len - left;

		copied = copy_to_iter(block, sizeof(block), iter);

		ret += copied;

		if (!iov_iter_count(iter) || copied != sizeof(block))

			break;

		}



		ubuf += block_len;

		ret += block_len;

		len -= block_len;

		if (!len)

			break;



		BUILD_BUG_ON(PAGE_SIZE % CHACHA_BLOCK_SIZE != 0);

		BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0);

		if (ret % PAGE_SIZE == 0) {

			if (signal_pending(current))

				break;
@@ -497,7 +490,7 @@ static ssize_t get_random_bytes_user(void __user *ubuf, size_t len) 
		}

	}



	memzero_explicit(output, sizeof(output));

	memzero_explicit(block, sizeof(block));

out_zero_chacha:

	memzero_explicit(chacha_state, sizeof(chacha_state));

	return ret ? ret : -EFAULT;
@@ -1224,6 +1217,10 @@ static void __cold try_to_generate_entropy(void) 


SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags)

{

	struct iov_iter iter;

	struct iovec iov;

	int ret;



	if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE))

		return -EINVAL;
@@ -1234,19 +1231,18 @@ SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags 
	if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM))

		return -EINVAL;



	if (len > INT_MAX)

		len = INT_MAX;



	if (!crng_ready() && !(flags & GRND_INSECURE)) {

		int ret;



		if (flags & GRND_NONBLOCK)

			return -EAGAIN;

		ret = wait_for_random_bytes();

		if (unlikely(ret))

			return ret;

	}

	return get_random_bytes_user(ubuf, len);



	ret = import_single_range(READ, ubuf, len, &iov, &iter);

	if (unlikely(ret))

		return ret;

	return get_random_bytes_user(&iter);

}



static __poll_t random_poll(struct file *file, poll_table *wait)
@@ -1290,8 +1286,7 @@ static ssize_t random_write(struct file *file, const char __user *ubuf, 
	return (ssize_t)len;

}



static ssize_t urandom_read(struct file *file, char __user *ubuf,

			    size_t len, loff_t *ppos)

static ssize_t urandom_read_iter(struct kiocb *kiocb, struct iov_iter *iter)

{

	static int maxwarn = 10;
@@ -1300,23 +1295,22 @@ static ssize_t urandom_read(struct file *file, char __user *ubuf, 
			++urandom_warning.missed;

		else if (ratelimit_disable || __ratelimit(&urandom_warning)) {

			--maxwarn;

			pr_notice("%s: uninitialized urandom read (%zd bytes read)\n",

				  current->comm, len);

			pr_notice("%s: uninitialized urandom read (%zu bytes read)\n",

				  current->comm, iov_iter_count(iter));

		}

	}



	return get_random_bytes_user(ubuf, len);

	return get_random_bytes_user(iter);

}



static ssize_t random_read(struct file *file, char __user *ubuf,

			   size_t len, loff_t *ppos)

static ssize_t random_read_iter(struct kiocb *kiocb, struct iov_iter *iter)

{

	int ret;



	ret = wait_for_random_bytes();

	if (ret != 0)

		return ret;

	return get_random_bytes_user(ubuf, len);

	return get_random_bytes_user(iter);

}



static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
@@ -1378,7 +1372,7 @@ static int random_fasync(int fd, struct file *filp, int on) 
}



const struct file_operations random_fops = {

	.read = random_read,

	.read_iter = random_read_iter,

	.write = random_write,

	.poll = random_poll,

	.unlocked_ioctl = random_ioctl,
@@ -1388,7 +1382,7 @@ const struct file_operations random_fops = { 
};



const struct file_operations urandom_fops = {

	.read = urandom_read,

	.read_iter = urandom_read_iter,

	.write = random_write,

	.unlocked_ioctl = random_ioctl,

	.compat_ioctl = compat_ptr_ioctl,