xsk: avoid store-tearing when assigning umem

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>

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 271d8d3..8c9056f 100644 (file)
--- 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;
        }