netdev - Re: [PATCH bpf-next V1] selftests/bpf: fix unmap bug in prog_tests/xdp

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Message-ID: <CAKH8qBt3XjsvhJfmkEpFxTOVPYNdLnrBOHZ9ekLM30hq6y4GEA@mail.gmail.com>
Date:   Wed, 1 Feb 2023 11:10:29 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, martin.lau@...nel.org,
        ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, dsahern@...il.com, willemb@...gle.com,
        void@...ifault.com, kuba@...nel.org, xdp-hints@...-project.net
Subject: Re: [PATCH bpf-next V1] selftests/bpf: fix unmap bug in prog_tests/xdp_metadata.c

On Wed, Feb 1, 2023 at 10:13 AM Jesper Dangaard Brouer
<brouer@...hat.com> wrote:
>
> The function close_xsk() unmap via munmap() the wrong memory pointer.
>
> The call xsk_umem__delete(xsk->umem) have already freed xsk->umem.
> Thus the call to munmap(xsk->umem, UMEM_SIZE) will have unpredictable
> behavior that can lead to Segmentation fault elsewhere, as man page
> explain subsequent references to these pages will generate SIGSEGV.
>
> Fixes: e2a46d54d7a1 ("selftests/bpf: Verify xdp_metadata xdp->af_xdp path")
> Reported-by: Martin KaFai Lau <martin.lau@...nel.org>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>

Good catch, thank you!

Acked-by: Stanislav Fomichev <sdf@...gle.com>

> ---
>  .../selftests/bpf/prog_tests/xdp_metadata.c        |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
> index e033d48288c0..241909d71c7e 100644
> --- a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
> @@ -121,7 +121,7 @@ static void close_xsk(struct xsk *xsk)
>                 xsk_umem__delete(xsk->umem);
>         if (xsk->socket)
>                 xsk_socket__delete(xsk->socket);
> -       munmap(xsk->umem, UMEM_SIZE);
> +       munmap(xsk->umem_area, UMEM_SIZE);
>  }
>
>  static void ip_csum(struct iphdr *iph)
>
>