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    Subject[PATCH 4.12 24/99] net: sched: fix NULL pointer dereference when action calls some targets
    Date
    4.12-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Xin Long <lucien.xin@gmail.com>


    [ Upstream commit 4f8a881acc9d1adaf1e552349a0b1df28933a04c ]

    As we know in some target's checkentry it may dereference par.entryinfo
    to check entry stuff inside. But when sched action calls xt_check_target,
    par.entryinfo is set with NULL. It would cause kernel panic when calling
    some targets.

    It can be reproduce with:
    # tc qd add dev eth1 ingress handle ffff:
    # tc filter add dev eth1 parent ffff: u32 match u32 0 0 action xt \
    -j ECN --ecn-tcp-remove

    It could also crash kernel when using target CLUSTERIP or TPROXY.

    By now there's no proper value for par.entryinfo in ipt_init_target,
    but it can not be set with NULL. This patch is to void all these
    panics by setting it with an ipt_entry obj with all members = 0.

    Note that this issue has been there since the very beginning.

    Signed-off-by: Xin Long <lucien.xin@gmail.com>
    Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/sched/act_ipt.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/net/sched/act_ipt.c
    +++ b/net/sched/act_ipt.c
    @@ -41,6 +41,7 @@ static int ipt_init_target(struct net *n
    {
    struct xt_tgchk_param par;
    struct xt_target *target;
    + struct ipt_entry e = {};
    int ret = 0;

    target = xt_request_find_target(AF_INET, t->u.user.name,
    @@ -52,6 +53,7 @@ static int ipt_init_target(struct net *n
    memset(&par, 0, sizeof(par));
    par.net = net;
    par.table = table;
    + par.entryinfo = &e;
    par.target = target;
    par.targinfo = t->data;
    par.hook_mask = hook;

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