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Date: Fri, 20 May 2022 11:44:57 +0200 From: "Jason A. Donenfeld" <Jason@...c4.com> To: Jens Axboe <axboe@...nel.dk>, Theodore Ts'o <tytso@....edu>, Christoph Hellwig <hch@....de>, LKML <linux-kernel@...r.kernel.org>, Al Viro <viro@...iv.linux.org.uk> Cc: "Jason A . Donenfeld" <Jason@...c4.com> Subject: [PATCH v4 1/3] random: convert to using fops->read_iter() From: Jens Axboe <axboe@...nel.dk> 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@...nel.dk> [Jason: rewrote get_random_bytes_user() to simplify and also incorporate additional suggestions from Al.] Cc: Al Viro <viro@...iv.linux.org.uk> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com> --- drivers/char/random.c | 55 +++++++++++++++++++------------------------ 1 file changed, 24 insertions(+), 31 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 0958fa91a964..f8cd747acec2 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -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 *to) { - size_t block_len, left, ret = 0; u32 chacha_state[CHACHA_STATE_WORDS]; u8 output[CHACHA_BLOCK_SIZE]; + size_t ret = 0, copied; - if (!len) + if (!iov_iter_count(to)) return 0; /* @@ -417,8 +417,8 @@ 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(to) <= CHACHA_KEY_SIZE) { + ret = copy_to_iter(&chacha_state[4], CHACHA_KEY_SIZE, to); goto out_zero_chacha; } @@ -427,17 +427,9 @@ static ssize_t get_random_bytes_user(void __user *ubuf, size_t len) 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(output, CHACHA_BLOCK_SIZE, to); + ret += copied; + if (!iov_iter_count(to) || copied != CHACHA_BLOCK_SIZE) break; BUILD_BUG_ON(PAGE_SIZE % CHACHA_BLOCK_SIZE != 0); @@ -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 to; + 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, &to); + if (unlikely(ret)) + return ret; + return get_random_bytes_user(&to); } 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 *to) { static int maxwarn = 10; @@ -1332,22 +1326,21 @@ static ssize_t urandom_read(struct file *file, char __user *ubuf, else if (ratelimit_disable || __ratelimit(&urandom_warning)) { --maxwarn; pr_notice("%s: uninitialized urandom read (%zd bytes read)\n", - current->comm, len); + current->comm, iov_iter_count(to)); } } - return get_random_bytes_user(ubuf, len); + return get_random_bytes_user(to); } -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 *to) { int ret; ret = wait_for_random_bytes(); if (ret != 0) return ret; - return get_random_bytes_user(ubuf, len); + return get_random_bytes_user(to); } 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, -- 2.35.1
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