[PATCHv2 net] net: sched: fix NULL pointer dereference when action calls some targets

[PATCHv2 net] net: sched: fix NULL pointer dereference when action calls some targets

[Xin Long]

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>
---
 net/sched/act_ipt.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/sched/act_ipt.c b/net/sched/act_ipt.c
index d516ba8..5417078 100644
--- a/net/sched/act_ipt.c
+++ b/net/sched/act_ipt.c
@@ -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;
-- 
2.1.0

Re: [PATCHv2 net] net: sched: fix NULL pointer dereference when action calls some targets

[Pablo Neira Ayuso]

On Fri, Aug 18, 2017 at 11:01:36AM +0800, Xin Long wrote:
> 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>

Re: [PATCHv2 net] net: sched: fix NULL pointer dereference when action calls some targets

[David Miller]

From: Xin Long <lucien.xin@gmail.com>
Date: Fri, 18 Aug 2017 11:01:36 +0800

> 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>

Applied and queued up for -stable, thanks.