From 9764f4b301c3e7eb3b75eec85b73cad449cdbb0d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= <bjorn.topel@intel.com>
Date: Wed, 4 Sep 2019 13:49:11 +0200
Subject: [PATCH] xsk: avoid store-tearing when assigning umem
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Git-commit: 9764f4b301c3e7eb3b75eec85b73cad449cdbb0d
Patch-mainline: v5.4-rc1
References: bsc#1111666

The umem member of struct xdp_sock is read outside of the control
mutex, in the mmap implementation, and needs a WRITE_ONCE to avoid
potential store-tearing.

Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Fixes: 423f38329d26 ("xsk: add umem fill queue support and mmap")
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 net/xdp/xsk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 271d8d3fb11e..8c9056f06989 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -644,7 +644,7 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 		}
 
 		xdp_get_umem(umem_xs->umem);
-		xs->umem = umem_xs->umem;
+		WRITE_ONCE(xs->umem, umem_xs->umem);
 		sockfd_put(sock);
 	} else if (!xs->umem || !xdp_umem_validate_queues(xs->umem)) {
 		err = -EINVAL;
@@ -751,7 +751,7 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
 
 		/* Make sure umem is ready before it can be seen by others */
 		smp_wmb();
-		xs->umem = umem;
+		WRITE_ONCE(xs->umem, umem);
 		mutex_unlock(&xs->mutex);
 		return 0;
 	}
-- 
2.16.4