Commit dd78b0c4 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

tty: implement read_iter 



Now that the ldisc read() function takes kernel pointers, it's fairly
straightforward to make the tty file operations use .read_iter() instead
of .read().

That automatically gives us vread() and friends, and also makes it
possible to do .splice_read() on ttys again.

Fixes: 36e2c742 ("fs: don't allow splice read/write without explicit ops")
Reported-by: default avatarOliver Giles <ohw.giles@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3b830a9c

drivers/tty/tty_io.c

+18 −18
Original line number Diff line number Diff line
@@ -142,7 +142,7 @@ LIST_HEAD(tty_drivers); /* linked list of tty drivers */ 
/* Mutex to protect creating and releasing a tty */

DEFINE_MUTEX(tty_mutex);



static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_read(struct kiocb *, struct iov_iter *);

static ssize_t tty_write(struct kiocb *, struct iov_iter *);

ssize_t redirected_tty_write(struct kiocb *, struct iov_iter *);

static __poll_t tty_poll(struct file *, poll_table *);
@@ -476,8 +476,9 @@ static void tty_show_fdinfo(struct seq_file *m, struct file *file) 


static const struct file_operations tty_fops = {

	.llseek		= no_llseek,

	.read		= tty_read,

	.read_iter	= tty_read,

	.write_iter	= tty_write,

	.splice_read	= generic_file_splice_read,

	.splice_write	= iter_file_splice_write,

	.poll		= tty_poll,

	.unlocked_ioctl	= tty_ioctl,
@@ -490,8 +491,9 @@ static const struct file_operations tty_fops = { 


static const struct file_operations console_fops = {

	.llseek		= no_llseek,

	.read		= tty_read,

	.read_iter	= tty_read,

	.write_iter	= redirected_tty_write,

	.splice_read	= generic_file_splice_read,

	.splice_write	= iter_file_splice_write,

	.poll		= tty_poll,

	.unlocked_ioctl	= tty_ioctl,
@@ -844,16 +846,17 @@ static void tty_update_time(struct timespec64 *time) 
 * data or clears the cookie. The cookie may be something that the

 * ldisc maintains state for and needs to free.

 */

static int iterate_tty_read(struct tty_ldisc *ld, struct tty_struct *tty, struct file *file,

		char __user *buf, size_t count)

static int iterate_tty_read(struct tty_ldisc *ld, struct tty_struct *tty,

		struct file *file, struct iov_iter *to)

{

	int retval = 0;

	void *cookie = NULL;

	unsigned long offset = 0;

	char kernel_buf[64];

	size_t count = iov_iter_count(to);



	do {

		int size, uncopied;

		int size, copied;



		size = count > sizeof(kernel_buf) ? sizeof(kernel_buf) : count;

		size = ld->ops->read(tty, file, kernel_buf, size, &cookie, offset);
@@ -869,10 +872,9 @@ static int iterate_tty_read(struct tty_ldisc *ld, struct tty_struct *tty, struct 
			return size;

		}



		uncopied = copy_to_user(buf+offset, kernel_buf, size);

		size -= uncopied;

		offset += size;

		count -= size;

		copied = copy_to_iter(kernel_buf, size, to);

		offset += copied;

		count -= copied;



		/*

		 * If the user copy failed, we still need to do another ->read()
@@ -880,7 +882,7 @@ static int iterate_tty_read(struct tty_ldisc *ld, struct tty_struct *tty, struct 
		 *

		 * But make sure size is zeroed.

		 */

		if (unlikely(uncopied)) {

		if (unlikely(copied != size)) {

			count = 0;

			retval = -EFAULT;

		}
@@ -907,10 +909,10 @@ static int iterate_tty_read(struct tty_ldisc *ld, struct tty_struct *tty, struct 
 *	read calls may be outstanding in parallel.

 */



static ssize_t tty_read(struct file *file, char __user *buf, size_t count,

			loff_t *ppos)

static ssize_t tty_read(struct kiocb *iocb, struct iov_iter *to)

{

	int i;

	struct file *file = iocb->ki_filp;

	struct inode *inode = file_inode(file);

	struct tty_struct *tty = file_tty(file);

	struct tty_ldisc *ld;
@@ -923,11 +925,9 @@ static ssize_t tty_read(struct file *file, char __user *buf, size_t count, 
	/* We want to wait for the line discipline to sort out in this

	   situation */

	ld = tty_ldisc_ref_wait(tty);

	if (!ld)

		return hung_up_tty_read(file, buf, count, ppos);

	i = -EIO;

	if (ld->ops->read)

		i = iterate_tty_read(ld, tty, file, buf, count);

	if (ld && ld->ops->read)

		i = iterate_tty_read(ld, tty, file, to);

	tty_ldisc_deref(ld);



	if (i > 0)
@@ -2927,7 +2927,7 @@ static long tty_compat_ioctl(struct file *file, unsigned int cmd, 


static int this_tty(const void *t, struct file *file, unsigned fd)

{

	if (likely(file->f_op->read != tty_read))

	if (likely(file->f_op->read_iter != tty_read))

		return 0;

	return file_tty(file) != t ? 0 : fd + 1;

}