[PATCH 4.9 46/95] nfit, address-range-scrub: fix scrub in-progress reporting

[Greg Kroah-Hartman]

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

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

From: Dan Williams <dan.j.williams@xxxxxxxxx>

commit 78727137fdf49edf9f731bde79d7189067b4047a upstream.

There is a small window whereby ARS scan requests can schedule work that
userspace will miss when polling scrub_show. Hold the init_mutex lock
over calls to report the status to close this potential escape. Also,
make sure that requests to cancel the ARS workqueue are treated as an
idle event.

Cc: <stable@xxxxxxxxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Fixes: 37b137ff8c83 ("nfit, libnvdimm: allow an ARS scrub...")
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/acpi/nfit/core.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -967,8 +967,11 @@ static ssize_t scrub_show(struct device
 	if (nd_desc) {
 		struct acpi_nfit_desc *acpi_desc = to_acpi_desc(nd_desc);
 
+		mutex_lock(&acpi_desc->init_mutex);
 		rc = sprintf(buf, "%d%s", acpi_desc->scrub_count,
-				(work_busy(&acpi_desc->work)) ? "+\n" : "\n");
+				work_busy(&acpi_desc->work)
+				&& !acpi_desc->cancel ? "+\n" : "\n");
+		mutex_unlock(&acpi_desc->init_mutex);
 	}
 	device_unlock(dev);
 	return rc;