net/sched: act_police: validate the control action inside init()

the following script:

 # tc qdisc add dev crash0 clsact
 # tc filter add dev crash0 egress matchall \
 > action police rate 3mbit burst 250k pass index 90
 # tc actions replace action police \
 > rate 3mbit burst 250k goto chain 42 index 90 cookie c1a0c1a0
 # tc actions show action police rate 3mbit burst

had the following output:

 Error: Failed to init TC action chain.
 We have an error talking to the kernel
 total acts 1

         action order 0:  police 0x5a rate 3Mbit burst 250Kb mtu 2Kb  action goto chain 42 overhead 0b
         ref 2 bind 1
         cookie c1a0c1a0

Then, when crash0 starts transmitting more than 3Mbit/s, the following
kernel crash is observed:

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
 #PF error: [normal kernel read fault]
 PGD 800000007a779067 P4D 800000007a779067 PUD 2ad96067 PMD 0
 Oops: 0000 [#1] SMP PTI
 CPU: 3 PID: 5032 Comm: netperf Not tainted 5.0.0-rc4.gotochain_crash+ #533
 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
 RIP: 0010:tcf_action_exec+0xb8/0x100
 Code: 00 00 00 20 74 1d 83 f8 03 75 09 49 83 c4 08 4d 39 ec 75 bc 48 83 c4 10 5b 5d 41 5c 41 5d 41 5e 41 5f c3 49 8b 97 a8 00 00 00 <48> 8b 12 48 89 55 00 48 83 c4 10 5b 5d 41 5c 41 5d 41 5e 41 5f c3
 RSP: 0018:ffffb0e04064fa60 EFLAGS: 00010246
 RAX: 000000002000002a RBX: ffff93bb3322cce0 RCX: 0000000000000005
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff93bb3322cce0
 RBP: ffffb0e04064fb00 R08: 0000000000000022 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000001 R12: ffff93bb3beed300
 R13: ffff93bb3beed308 R14: 0000000000000001 R15: ffff93bb3b64d000
 FS:  00007f0bc6be5740(0000) GS:ffff93bb3db80000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 00000000746a8001 CR4: 00000000001606e0
 Call Trace:
  tcf_classify+0x58/0x120
  __dev_queue_xmit+0x40a/0x890
  ? ipt_do_table+0x31c/0x420 [ip_tables]
  ? ip_finish_output2+0x16f/0x430
  ip_finish_output2+0x16f/0x430
  ? ip_output+0x69/0xe0
  ip_output+0x69/0xe0
  ? ip_forward_options+0x1a0/0x1a0
  __tcp_transmit_skb+0x563/0xa40
  tcp_write_xmit+0x243/0xfa0
  __tcp_push_pending_frames+0x32/0xf0
  tcp_sendmsg_locked+0x404/0xd30
  tcp_sendmsg+0x27/0x40
  sock_sendmsg+0x36/0x40
  __sys_sendto+0x10e/0x140
  ? __sys_connect+0x87/0xf0
  ? syscall_trace_enter+0x1df/0x2e0
  ? __audit_syscall_exit+0x216/0x260
  __x64_sys_sendto+0x24/0x30
  do_syscall_64+0x5b/0x180
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f0bc5ffbafd
 Code: 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 8b 05 ae c4 2c 00 85 c0 75 2d 45 31 c9 45 31 c0 4c 63 d1 48 63 ff b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 8b 15 63 63 2c 00 f7 d8 64 89 02 48
 RSP: 002b:00007fffef94b7f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
 RAX: ffffffffffffffda RBX: 0000000000004000 RCX: 00007f0bc5ffbafd
 RDX: 0000000000004000 RSI: 00000000017e5420 RDI: 0000000000000004
 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
 R13: 00000000017e51d0 R14: 0000000000000010 R15: 0000000000000006
 Modules linked in: act_police veth ip6table_filter ip6_tables iptable_filter binfmt_misc ext4 snd_hda_codec_generic mbcache crct10dif_pclmul jbd2 crc32_pclmul ghash_clmulni_intel snd_hda_intel snd_hda_codec snd_hwdep snd_hda_core snd_seq snd_seq_device snd_pcm aesni_intel crypto_simd cryptd glue_helper snd_timer snd joydev pcspkr virtio_balloon soundcore i2c_piix4 nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs ata_generic pata_acpi qxl drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm virtio_blk virtio_net virtio_console net_failover failover crc32c_intel ata_piix libata serio_raw virtio_pci virtio_ring virtio floppy dm_mirror dm_region_hash dm_log dm_mod
 CR2: 0000000000000000

Validating the control action within tcf_police_init() proved to fix the
above issue. A TDC selftest is added to verify the correct behavior.

Fixes: db50514f ("net: sched: add termination action to allow goto chain")
Fixes: 97763dc0 ("net_sched: reject unknown tcfa_action values")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_police.c

@@ -21,6 +21,7 @@
 #include <linux/slab.h>
 #include <net/act_api.h>
 #include <net/netlink.h>
+#include <net/pkt_cls.h>
 
 struct tcf_police_params {
 	int			tcfp_result;
@@ -88,6 +89,7 @@ static int tcf_police_init(struct net *net, struct nlattr *nla,
 {
 	int ret = 0, tcfp_result = TC_ACT_OK, err, size;
 	struct nlattr *tb[TCA_POLICE_MAX + 1];
+	struct tcf_chain *goto_ch = NULL;
 	struct tc_police *parm;
 	struct tcf_police *police;
 	struct qdisc_rate_table *R_tab = NULL, *P_tab = NULL;
@@ -129,6 +131,9 @@ static int tcf_police_init(struct net *net, struct nlattr *nla,
 		tcf_idr_release(*a, bind);
 		return -EEXIST;
 	}
+	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
+	if (err < 0)
+		goto release_idr;
 
 	police = to_police(*a);
 	if (parm->rate.rate) {
@@ -214,12 +219,14 @@ static int tcf_police_init(struct net *net, struct nlattr *nla,
 	if (new->peak_present)
 		police->tcfp_ptoks = new->tcfp_mtu_ptoks;
 	spin_unlock_bh(&police->tcfp_lock);
-	police->tcf_action = parm->action;
+	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 	rcu_swap_protected(police->params,
 			   new,
 			   lockdep_is_held(&police->tcf_lock));
 	spin_unlock_bh(&police->tcf_lock);
 
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
 	if (new)
 		kfree_rcu(new, rcu);
 
@@ -230,6 +237,9 @@ static int tcf_police_init(struct net *net, struct nlattr *nla,
 failure:
 	qdisc_put_rtab(P_tab);
 	qdisc_put_rtab(R_tab);
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+release_idr:
 	tcf_idr_release(*a, bind);
 	return err;
 }

tools/testing/selftests/tc-testing/tc-tests/actions/police.json

@@ -739,5 +739,30 @@
         "teardown": [
             "$TC actions flush action police"
         ]
+    },
+    {
+        "id": "689e",
+        "name": "Replace police action with invalid goto chain control",
+        "category": [
+            "actions",
+            "police"
+        ],
+        "setup": [
+            [
+                "$TC actions flush action police",
+                0,
+                1,
+                255
+            ],
+            "$TC actions add action police rate 3mbit burst 250k drop index 90"
+        ],
+        "cmdUnderTest": "$TC actions replace action police rate 3mbit burst 250k goto chain 42 index 90 cookie c1a0c1a0",
+        "expExitCode": "255",
+        "verifyCmd": "$TC actions get action police index 90",
+        "matchPattern": "action order [0-9]*:  police 0x5a rate 3Mbit burst 250Kb mtu 2Kb action drop",
+        "matchCount": "1",
+        "teardown": [
+            "$TC actions flush action police"
+        ]
     }
 ]