linux-kernel - [PATCH 4.20 021/183] pvcalls-front: read all data before closing the connection

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Date:   Mon, 25 Feb 2019 22:09:54 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stefano Stabellini <stefanos@...inx.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.20 021/183] pvcalls-front: read all data before closing the connection

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

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

[ Upstream commit b79470b64fa9266948d1ce8d825ced94c4f63293 ]

When a connection is closing in_error is set to ENOTCONN. There could
still be outstanding data on the ring left by the backend. Before
closing the connection on the frontend side, drain the ring.

Signed-off-by: Stefano Stabellini <stefanos@...inx.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/xen/pvcalls-front.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 77224d8f3e6fe..e5d95aab2cb80 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -560,15 +560,13 @@ static int __read_ring(struct pvcalls_data_intf *intf,
 	error = intf->in_error;
 	/* get pointers before reading from the ring */
 	virt_rmb();
-	if (error < 0)
-		return error;
 
 	size = pvcalls_queued(prod, cons, array_size);
 	masked_prod = pvcalls_mask(prod, array_size);
 	masked_cons = pvcalls_mask(cons, array_size);
 
 	if (size == 0)
-		return 0;
+		return error ?: size;
 
 	if (len > size)
 		len = size;
-- 
2.19.1