Patch "tty: fix __tty_insert_flip_char regression" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

tty: fix __tty_insert_flip_char regression

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tty-fix-__tty_insert_flip_char-regression.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Arnd Bergmann <[email protected]>
Date: Wed, 2 Aug 2017 13:11:39 +0200
Subject: tty: fix __tty_insert_flip_char regression

From: Arnd Bergmann <[email protected]>

commit 8a5a90a2a477b86a3dc2eaa5a706db9bfdd647ca upstream.

Sergey noticed a small but fatal mistake in __tty_insert_flip_char, leading to an oops in an interrupt handler when using any serial port.

The problem is that I accidentally took the tty_buffer pointer before calling __tty_buffer_request_room(), which replaces the buffer. This moves the pointer lookup to the right place after allocating the new buffer space.

---
 drivers/tty/tty_buffer.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -372,12 +372,13 @@ EXPORT_SYMBOL(tty_insert_flip_string_fla
  */
 int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
 {
-	struct tty_buffer *tb = port->buf.tail;
+	struct tty_buffer *tb;
 	int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
 
 	if (!__tty_buffer_request_room(port, 1, flags))
 		return 0;
 
+	tb = port->buf.tail;
 	if (~tb->flags & TTYB_NORMAL)
 		*flag_buf_ptr(tb, tb->used) = flag;
 	*char_buf_ptr(tb, tb->used++) = ch;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/qlge-avoid-memcpy-buffer-overflow.patch queue-4.4/tty-fix-__tty_insert_flip_char-regression.patch queue-4.4/tty-improve-tty_insert_flip_char-fast-path.patch queue-4.4/tty-improve-tty_insert_flip_char-slow-path.patch

Hmm I thought I had sent a backported version for stable that just contains the 'fast path' plus with the bugfix, but I must have forgotten to actually send it out.

Anyway, taking all three patches for stable should also work, no need to revisit unless you would prefer to drop the 'slow path' patch.

Arnd

Keeping in sync is good, I'll just take all 3, thanks.

greg k-h