Alan,

Thank you, updated fix (tested on bits based on commit 
bdc0077af574800d24318b6945cf2344e8dbb050) is attached.
Is this correct now?

Thanks and regards,
-Stanislav Kozina

>> You mean call to tty_put_user(), correct? Thanks for this catch.
>> So what about to unlock the lock for this time? Because we need to hold
>> the lock while checking tty->read_cnt in the while loop condition, correct?
> I think you are right on that yes.
>
> Alan