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Donenfeld" To: Jens Axboe , LKML Cc: "Jason A . Donenfeld" Subject: [PATCH v3 1/3] random: convert to using fops->read_iter() Date: Fri, 20 May 2022 02:40:56 +0200 Message-Id: <20220520004058.96691-2-Jason@zx2c4.com> In-Reply-To: <20220520004058.96691-1-Jason@zx2c4.com> References: <20220520004058.96691-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jens Axboe This is a pre-requisite to writing up splice() again for the random and urandom drivers. Signed-off-by: Jens Axboe [Jason: simplify control flow a bit in get_random_bytes_user().] Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 49 ++++++++++++++++++++----------------------- 1 file changed, 23 insertions(+), 26 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 0958fa91a964..2b2c3681f172 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; - if (!len) + if (!iov_iter_count(to)) return 0; /* @@ -417,27 +417,21 @@ 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], iov_iter_count(to), to); goto out_zero_chacha; } for (;;) { + size_t copied, block_len = min_t(size_t, iov_iter_count(to), CHACHA_BLOCK_SIZE); + chacha20_block(chacha_state, output); 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, block_len, to); + ret += copied; + if (!iov_iter_count(to) || copied != block_len) break; BUILD_BUG_ON(PAGE_SIZE % CHACHA_BLOCK_SIZE != 0); @@ -1248,6 +1242,9 @@ static void __cold try_to_generate_entropy(void) SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags) { + struct iovec iov = { .iov_base = ubuf }; + struct iov_iter iter; + if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE)) return -EINVAL; @@ -1270,7 +1267,9 @@ SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags if (unlikely(ret)) return ret; } - return get_random_bytes_user(ubuf, len); + iov.iov_len = len; + iov_iter_init(&iter, READ, &iov, 1, len); + return get_random_bytes_user(&iter); } static __poll_t random_poll(struct file *file, poll_table *wait) @@ -1314,8 +1313,7 @@ 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 +1330,21 @@ 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 +1406,7 @@ 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 +1416,7 @@ 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