net/sched: fix a couple of splats in the error path of tfc_gate_init()

trying to configure TC 'act_gate' rules with invalid control actions, the
following splat can be observed:

 general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN NOPTI
 KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
 CPU: 1 PID: 2143 Comm: tc Not tainted 5.7.0-rc6+ #168
 Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
 RIP: 0010:hrtimer_active+0x56/0x290
 [...]
  Call Trace:
  hrtimer_try_to_cancel+0x6d/0x330
  hrtimer_cancel+0x11/0x20
  tcf_gate_cleanup+0x15/0x30 [act_gate]
  tcf_action_cleanup+0x58/0x170
  __tcf_action_put+0xb0/0xe0
  __tcf_idr_release+0x68/0x90
  tcf_gate_init+0x7c7/0x19a0 [act_gate]
  tcf_action_init_1+0x60f/0x960
  tcf_action_init+0x157/0x2a0
  tcf_action_add+0xd9/0x2f0
  tc_ctl_action+0x2a3/0x39d
  rtnetlink_rcv_msg+0x5f3/0x920
  netlink_rcv_skb+0x121/0x350
  netlink_unicast+0x439/0x630
  netlink_sendmsg+0x714/0xbf0
  sock_sendmsg+0xe2/0x110
  ____sys_sendmsg+0x5b4/0x890
  ___sys_sendmsg+0xe9/0x160
  __sys_sendmsg+0xd3/0x170
  do_syscall_64+0x9a/0x370
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

this is caused by hrtimer_cancel(), running before hrtimer_init(). Fix it
ensuring to call hrtimer_cancel() only if clockid is valid, and the timer
has been initialized. After fixing this splat, the same error path causes
another problem:

 general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
 KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
 CPU: 1 PID: 980 Comm: tc Not tainted 5.7.0-rc6+ #168
 Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
 RIP: 0010:release_entry_list+0x4a/0x240 [act_gate]
 [...]
 Call Trace:
  tcf_action_cleanup+0x58/0x170
  __tcf_action_put+0xb0/0xe0
  __tcf_idr_release+0x68/0x90
  tcf_gate_init+0x7ab/0x19a0 [act_gate]
  tcf_action_init_1+0x60f/0x960
  tcf_action_init+0x157/0x2a0
  tcf_action_add+0xd9/0x2f0
  tc_ctl_action+0x2a3/0x39d
  rtnetlink_rcv_msg+0x5f3/0x920
  netlink_rcv_skb+0x121/0x350
  netlink_unicast+0x439/0x630
  netlink_sendmsg+0x714/0xbf0
  sock_sendmsg+0xe2/0x110
  ____sys_sendmsg+0x5b4/0x890
  ___sys_sendmsg+0xe9/0x160
  __sys_sendmsg+0xd3/0x170
  do_syscall_64+0x9a/0x370
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

the problem is similar: tcf_action_cleanup() was trying to release a list
without initializing it first. Ensure that INIT_LIST_HEAD() is called for
every newly created 'act_gate' action, same as what was done to 'act_ife'
with commit 44c23d71 ("net/sched: act_ife: initalize ife->metalist
earlier").

Fixes: a51c328d ("net: qos: introduce a gate control flow action")
CC: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: NDavide Caratti <dcaratti@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/act_gate.c

@@ -331,6 +331,10 @@ static int tcf_gate_init(struct net *net, struct nlattr *nla,
 		tcf_idr_release(*a, bind);
 		return -EEXIST;
 	}
+	if (ret == ACT_P_CREATED) {
+		to_gate(*a)->param.tcfg_clockid = -1;
+		INIT_LIST_HEAD(&(to_gate(*a)->param.entries));
+	}
 
 	if (tb[TCA_GATE_PRIORITY])
 		prio = nla_get_s32(tb[TCA_GATE_PRIORITY]);
@@ -377,7 +381,6 @@ static int tcf_gate_init(struct net *net, struct nlattr *nla,
 			goto chain_put;
 	}
 
-	INIT_LIST_HEAD(&p->entries);
 	if (tb[TCA_GATE_ENTRY_LIST]) {
 		err = parse_gate_list(tb[TCA_GATE_ENTRY_LIST], p, extack);
 		if (err < 0)
@@ -449,9 +452,9 @@ static void tcf_gate_cleanup(struct tc_action *a)
 	struct tcf_gate *gact = to_gate(a);
 	struct tcf_gate_params *p;
 
-	hrtimer_cancel(&gact->hitimer);
-
 	p = &gact->param;
+	if (p->tcfg_clockid != -1)
+		hrtimer_cancel(&gact->hitimer);
 
 	release_entry_list(&p->entries);
 }