From: Jens Axboe axboe@kernel.dk
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: 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 66 ++++++++++++++++++++++---------------------------- 1 file changed, 30 insertions(+), 36 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -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 } 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(voi * 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; @@ -497,7 +490,7 @@ static ssize_t get_random_bytes_user(voi } }
- 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_entro
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 * 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 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 ++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 }
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,