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    Subject[PATCH 4.19 544/639] xsk: avoid store-tearing when assigning umem
    Date
    From: Björn Töpel <bjorn.topel@intel.com>

    [ 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@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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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


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