linux-kernel - [PATCH 4.9 25/41] staging: comedi: comedi_fops: do not call blocking ops when !TASK

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Date:   Mon, 14 Aug 2017 18:18:35 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Piotr Gregor <piotrgregor@...ncme.org>,
        Ian Abbott <abbotti@....co.uk>
Subject: [PATCH 4.9 25/41] staging: comedi: comedi_fops: do not call blocking ops when !TASK_RUNNING

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ian Abbott <abbotti@....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@...ncme.org>
Signed-off-by: Ian Abbott <abbotti@....co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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;