[net,2/4] net/sched: act_police: disallow 'goto chain' on fallback control action

in the following command:

 # tc action add action police rate <r> burst <b> conform-exceed <c1>/<c2>

'goto chain x' is allowed only for c1: setting it for c2 makes the kernel
crash with NULL pointer dereference, since TC core doesn't initialize the
chain handle.

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
---
 net/sched/act_police.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

On Sat, Oct 20, 2018 at 2:33 PM Davide Caratti <dcaratti@redhat.com> wrote:
>
> in the following command:
>
>  # tc action add action police rate <r> burst <b> conform-exceed <c1>/<c2>
>
> 'goto chain x' is allowed only for c1: setting it for c2 makes the kernel
> crash with NULL pointer dereference, since TC core doesn't initialize the
> chain handle.
>
> Signed-off-by: Davide Caratti <dcaratti@redhat.com>

Acked-by: Cong Wang <xiyou.wangcong@gmail.com>

Sat, Oct 20, 2018 at 11:33:08PM CEST, dcaratti@redhat.com wrote:
>in the following command:
>
> # tc action add action police rate <r> burst <b> conform-exceed <c1>/<c2>
>
>'goto chain x' is allowed only for c1: setting it for c2 makes the kernel
>crash with NULL pointer dereference, since TC core doesn't initialize the
>chain handle.
>
>Signed-off-by: Davide Caratti <dcaratti@redhat.com>
>---
> net/sched/act_police.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
>diff --git a/net/sched/act_police.c b/net/sched/act_police.c
>index 5d8bfa878477..3b793393efd1 100644
>--- a/net/sched/act_police.c
>+++ b/net/sched/act_police.c
>@@ -150,6 +150,16 @@ static int tcf_police_init(struct net *net, struct nlattr *nla,
> 		goto failure;
> 	}
> 
>+	if (tb[TCA_POLICE_RESULT]) {
>+		police->tcfp_result = nla_get_u32(tb[TCA_POLICE_RESULT]);
>+		if (TC_ACT_EXT_CMP(police->tcfp_result, TC_ACT_GOTO_CHAIN)) {
>+			NL_SET_ERR_MSG(extack,
>+				       "goto chain not allowed on fallback");

Also, no need for line-wrap

Acked-by: Jiri Pirko <jiri@mellanox.com>



>+			err = -EINVAL;
>+			goto failure;
>+		}
>+	}
>+
> 	spin_lock_bh(&police->tcf_lock);
> 	/* No failure allowed after this point */
> 	police->tcfp_mtu = parm->mtu;
>@@ -173,8 +183,6 @@ static int tcf_police_init(struct net *net, struct nlattr *nla,
> 		police->peak_present = false;
> 	}
> 
>-	if (tb[TCA_POLICE_RESULT])
>-		police->tcfp_result = nla_get_u32(tb[TCA_POLICE_RESULT]);
> 	police->tcfp_burst = PSCHED_TICKS2NS(parm->burst);
> 	police->tcfp_toks = police->tcfp_burst;
> 	if (police->peak_present) {
>-- 
>2.17.1
>