[PATCH 4.19 544/639] xsk: avoid store-tearing when assigning umem

[Greg Kroah-Hartman]

From: BjÃrn TÃpel <bjorn.topel@xxxxxxxxx>

[ Upstream commit 9764f4b301c3e7eb3b75eec85b73cad449cdbb0d ]

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@xxxxxxxxx>
Fixes: 423f38329d26 ("xsk: add umem fill queue support and mmap")
Signed-off-by: BjÃrn TÃpel <bjorn.topel@xxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 b580078f04d15..72caa4fb13f47 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -454,7 +454,7 @@ 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;
@@ -534,7 +534,7 @@ 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;
 	}
-- 
2.20.1