linux-kernel - [PATCH v3] uwb: properly check kthread

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Message-Id: <45066f5bb1964dcbd80562bdc4317a3a6af36fd0.1505392106.git.andreyknvl@google.com>
Date:   Thu, 14 Sep 2017 14:30:55 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>,
        "Gustavo A . R . Silva" <garsilva@...eddedor.com>,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH v3] uwb: properly check kthread_run return value

uwbd_start() calls kthread_run() and checks that the return value is
not NULL. But the return value is not NULL in case kthread_run() fails,
it takes the form of ERR_PTR(-EINTR).

Use IS_ERR() instead.

Also add a check to uwbd_stop().

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---

v2: don't assign error values to rc->uwbd.task.
v1: added a check to uwbd_stop().

---
 drivers/uwb/uwbd.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/uwb/uwbd.c b/drivers/uwb/uwbd.c
index 01c20a260a8b..39dd4ef53c77 100644
--- a/drivers/uwb/uwbd.c
+++ b/drivers/uwb/uwbd.c
@@ -302,18 +302,22 @@ static int uwbd(void *param)
 /** Start the UWB daemon */
 void uwbd_start(struct uwb_rc *rc)
 {
-	rc->uwbd.task = kthread_run(uwbd, rc, "uwbd");
-	if (rc->uwbd.task == NULL)
+	struct task_struct *task = kthread_run(uwbd, rc, "uwbd");
+	if (IS_ERR(task)) {
+		rc->uwbd.task = NULL;
 		printk(KERN_ERR "UWB: Cannot start management daemon; "
 		       "UWB won't work\n");
-	else
+	} else {
+		rc->uwbd.task = task;
 		rc->uwbd.pid = rc->uwbd.task->pid;
+	}
 }
 
 /* Stop the UWB daemon and free any unprocessed events */
 void uwbd_stop(struct uwb_rc *rc)
 {
-	kthread_stop(rc->uwbd.task);
+	if (rc->uwbd.task)
+		kthread_stop(rc->uwbd.task);
 	uwbd_flush(rc);
 }
 
-- 
2.14.1.690.gbb1197296e-goog