linux-kernel - [PATCH 4.19 543/639] xsk: avoid store-tearing when assigning queues

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Message-Id: <20200124093157.095033868@linuxfoundation.org>
Date:   Fri, 24 Jan 2020 10:31:53 +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, Jonathan Lemon <jonathan.lemon@...il.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 543/639] xsk: avoid store-tearing when assigning queues

From: Björn Töpel <bjorn.topel@...el.com>

[ Upstream commit 94a997637c5b562fa0ca44fca1d2cd02ec08236f ]

Use WRITE_ONCE when doing the store of tx, rx, fq, and cq, to avoid
potential store-tearing. These members are read outside of the control
mutex in the mmap implementation.

Acked-by: Jonathan Lemon <jonathan.lemon@...il.com>
Fixes: 37b076933a8e ("xsk: add missing write- and data-dependency barrier")
Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/xdp/xsk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index c90854bc3048e..b580078f04d15 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -320,7 +320,7 @@ static int xsk_init_queue(u32 entries, struct xsk_queue **queue,
 
 	/* Make sure queue is ready before it can be seen by others */
 	smp_wmb();
-	*queue = q;
+	WRITE_ONCE(*queue, q);
 	return 0;
 }
 
-- 
2.20.1