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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Timur Celik <mail@timurcelik.de>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.19 38/68] tun: fix blocking read
Date:   Fri,  8 Mar 2019 13:50:08 +0100
Message-Id: <20190308124912.605311900@linuxfoundation.org>
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4.19-stable review patch.  If anyone has any objections, please let me know.

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

From: Timur Celik <mail@timurcelik.de>

[ Upstream commit 71828b2240692cec0e68b8d867bc00e1745e7fae ]

This patch moves setting of the current state into the loop. Otherwise
the task may end up in a busy wait loop if none of the break conditions
are met.

Signed-off-by: Timur Celik <mail@timurcelik.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/tun.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2122,9 +2122,9 @@ static void *tun_ring_recv(struct tun_fi
 	}
 
 	add_wait_queue(&tfile->wq.wait, &wait);
-	current->state = TASK_INTERRUPTIBLE;
 
 	while (1) {
+		set_current_state(TASK_INTERRUPTIBLE);
 		ptr = ptr_ring_consume(&tfile->tx_ring);
 		if (ptr)
 			break;
@@ -2140,7 +2140,7 @@ static void *tun_ring_recv(struct tun_fi
 		schedule();
 	}
 
-	current->state = TASK_RUNNING;
+	set_current_state(TASK_RUNNING);
 	remove_wait_queue(&tfile->wq.wait, &wait);
 
 out: