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random: convert to using fops->read_iter()

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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: Jens 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: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jens Axboe 2022-05-19 17:31:36 -06:00 committed by Jason A. Donenfeld
parent 3092adcef3
commit 1b388e7765
1 changed files with 29 additions and 36 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

65
drivers/char/random.c
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@ -397,13 +397,13 @@ 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_STATE_WORDS];
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;
/*
@ -417,30 +417,22 @@ 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;
break;
}
ubuf += block_len;
ret += block_len;
len -= block_len;
if (!len)
copied = copy_to_iter(block, sizeof(block), iter);
ret += copied;
if (!iov_iter_count(iter) || copied != sizeof(block))
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;
@ -448,7 +440,7 @@ 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;
@ -1248,6 +1240,10 @@ 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;
@ -1258,19 +1254,18 @@ 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)
@ -1314,8 +1309,7 @@ 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;
@ -1331,23 +1325,22 @@ 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)
@ -1409,7 +1402,7 @@ 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,
@ -1419,7 +1412,7 @@ 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,