Patch "serdev: fix receive_buf return value when no callback" has been added to the 4.14-stable tree

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

serdev: fix receive_buf return value when no callback

to the 4.14-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:
serdev-fix-receive_buf-return-value-when-no-callback.patch
and it can be found in the queue-4.14 subdirectory.

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

From: Johan Hovold <[email protected]>
Date: Fri, 3 Nov 2017 15:30:53 +0100
Subject: serdev: fix receive_buf return value when no callback

From: Johan Hovold <[email protected]>

[ Upstream commit fd00cf81a9a84776ba58e56bd042c726dcf75cf3 ]

The receive_buf callback is supposed to return the number of bytes processed and should specifically not return a negative errno.

Due to missing sanity checks in the serdev tty-port controller, a driver not providing a receive_buf callback could cause the flush_to_ldisc() worker to spin in a tight loop when the tty buffer pointers are incremented with -EINVAL (-22).

The missing sanity checks have now been added to the tty-port controller, but let's fix up the serdev-controller helper as well.

---
 include/linux/serdev.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -184,7 +184,7 @@ static inline int serdev_controller_rece
 	struct serdev_device *serdev = ctrl->serdev;
 
 	if (!serdev || !serdev->ops->receive_buf)
-		return -EINVAL;
+		return 0;
 
 	return serdev->ops->receive_buf(serdev, data, count);
 }

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

queue-4.14/serdev-fix-receive_buf-return-value-when-no-callback.patch