[PATCH 4.9 25/41] staging: comedi: comedi_fops: do not call blocking ops when !TASK_RUNNING

Greg Kroah-Hartman
2017-08-15T01:39:11Z

From: Ian Abbott <abbotti@mev.co.uk>

commit cef988642cdac44e910a27cb6e8166c96f86a0df upstream.

Comedi's read and write file operation handlers (`comedi_read()` and
`comedi_write()`) currently call `copy_to_user()` or `copy_from_user()`
whilst in the `TASK_INTERRUPTIBLE` state, which falls foul of the
`might_fault()` checks when enabled. Fix it by setting the current task
state back to `TASK_RUNNING` a bit earlier before calling these
functions.

Reported-by: Piotr Gregor <piotrgregor@rsyncme.org>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/comedi/comedi_fops.c | 3 +++
1 file changed, 3 insertions(+)

--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -2385,6 +2385,7 @@ static ssize_t comedi_write(struct file
continue;
}

+ set_current_state(TASK_RUNNING);
wp = async->buf_write_ptr;
n1 = min(n, async->prealloc_bufsz - wp);
n2 = n - n1;
@@ -2517,6 +2518,8 @@ static ssize_t comedi_read(struct file *
}
continue;
}
+
+ set_current_state(TASK_RUNNING);
rp = async->buf_read_ptr;
n1 = min(n, async->prealloc_bufsz - rp);
n2 = n - n1;