[PATCH 5.10 189/199] tty: fix up hung_up_tty_write() conversion

[Greg Kroah-Hartman]

From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

commit 17749851eb9ca2298e7c3b81aae4228961b36f28 upstream.

In commit "tty: implement write_iter", I left the write_iter conversion
of the hung up tty case alone, because I incorrectly thought it didn't
matter.

Jiri showed me the errors of my ways, and pointed out the problems with
that incomplete conversion.  Fix it all up.

Reported-by: Jiri Slaby <jirislaby@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Jiri Slaby <jirislaby@xxxxxxxxxx>
Link: https://lore.kernel.org/r/CAHk-=wh+-rGsa=xruEWdg_fJViFG8rN9bpLrfLz=_yBYh2tBhA@xxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/tty/tty_io.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -437,8 +437,7 @@ static ssize_t hung_up_tty_read(struct f
 	return 0;
 }
 
-static ssize_t hung_up_tty_write(struct file *file, const char __user *buf,
-				 size_t count, loff_t *ppos)
+static ssize_t hung_up_tty_write(struct kiocb *iocb, struct iov_iter *from)
 {
 	return -EIO;
 }
@@ -504,7 +503,7 @@ static const struct file_operations cons
 static const struct file_operations hung_up_tty_fops = {
 	.llseek		= no_llseek,
 	.read		= hung_up_tty_read,
-	.write		= hung_up_tty_write,
+	.write_iter	= hung_up_tty_write,
 	.poll		= hung_up_tty_poll,
 	.unlocked_ioctl	= hung_up_tty_ioctl,
 	.compat_ioctl	= hung_up_tty_compat_ioctl,
@@ -1045,7 +1044,9 @@ static ssize_t tty_write(struct kiocb *i
 	if (tty->ops->write_room == NULL)
 		tty_err(tty, "missing write_room method\n");
 	ld = tty_ldisc_ref_wait(tty);
-	if (!ld || !ld->ops->write)
+	if (!ld)
+		return hung_up_tty_write(iocb, from);
+	if (!ld->ops->write)
 		ret = -EIO;
 	else
 		ret = do_tty_write(ld->ops->write, tty, file, from);