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    Subject[PATCH 4.19 39/79] erspan: fix the tun_info options_len check for erspan
    Date
    From: Xin Long <lucien.xin@gmail.com>

    [ Upstream commit 2eb8d6d2910cfe3dc67dc056f26f3dd9c63d47cd ]

    The check for !md doens't really work for ip_tunnel_info_opts(info) which
    only does info + 1. Also to avoid out-of-bounds access on info, it should
    ensure options_len is not less than erspan_metadata in both erspan_xmit()
    and ip6erspan_tunnel_xmit().

    Fixes: 1a66a836da ("gre: add collect_md mode to ERSPAN tunnel")
    Signed-off-by: Xin Long <lucien.xin@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv4/ip_gre.c | 4 ++--
    net/ipv6/ip6_gre.c | 4 ++--
    2 files changed, 4 insertions(+), 4 deletions(-)

    --- a/net/ipv4/ip_gre.c
    +++ b/net/ipv4/ip_gre.c
    @@ -589,9 +589,9 @@ static void erspan_fb_xmit(struct sk_buf
    key = &tun_info->key;
    if (!(tun_info->key.tun_flags & TUNNEL_ERSPAN_OPT))
    goto err_free_rt;
    + if (tun_info->options_len < sizeof(*md))
    + goto err_free_rt;
    md = ip_tunnel_info_opts(tun_info);
    - if (!md)
    - goto err_free_rt;

    /* ERSPAN has fixed 8 byte GRE header */
    version = md->version;
    --- a/net/ipv6/ip6_gre.c
    +++ b/net/ipv6/ip6_gre.c
    @@ -1000,9 +1000,9 @@ static netdev_tx_t ip6erspan_tunnel_xmit
    dsfield = key->tos;
    if (!(tun_info->key.tun_flags & TUNNEL_ERSPAN_OPT))
    goto tx_err;
    - md = ip_tunnel_info_opts(tun_info);
    - if (!md)
    + if (tun_info->options_len < sizeof(*md))
    goto tx_err;
    + md = ip_tunnel_info_opts(tun_info);

    tun_id = tunnel_id_to_key32(key->tun_id);
    if (md->version == 1) {

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