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net: sched: fix NULL pointer dereference when action calls some targets

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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>
This commit is contained in:
Xin Long 2017-08-18 11:01:36 +08:00 committed by David S. Miller
parent 9a19bad70c
commit 4f8a881acc
1 changed files with 2 additions and 0 deletions
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2
net/sched/act_ipt.c
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@ -41,6 +41,7 @@ static int ipt_init_target(struct net *net, struct xt_entry_target *t,
{
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 *net, struct xt_entry_target *t,
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;