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

the following script:

 # tc qdisc add dev crash0 clsact
 # tc filter add dev crash0 egress matchall \
 > action simple sdata hello pass index 90
 # tc actions replace action simple \
 > sdata world goto chain 42 index 90 cookie c1a0c1a0
 # tc action show action simple

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: Simple <world>
          index 90 ref 2 bind 1
         cookie c1a0c1a0

Then, the first packet transmitted by crash0 made the kernel crash:

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
 #PF error: [normal kernel read fault]
 PGD 800000006a6fb067 P4D 800000006a6fb067 PUD 6aed6067 PMD 0
 Oops: 0000 [#1] SMP PTI
 CPU: 2 PID: 3241 Comm: kworker/2:0 Not tainted 5.0.0-rc4.gotochain_crash+ torvalds#536
 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
 Workqueue: ipv6_addrconf addrconf_dad_work
 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:ffffbe6781763ad0 EFLAGS: 00010246
 RAX: 000000002000002a RBX: ffff9e59bdb80e00 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: ffff9e59b4716738 RDI: ffff9e59ab12d140
 RBP: ffffbe6781763b70 R08: 0000000000000234 R09: 0000000000aaaaaa
 R10: 0000000000000000 R11: ffff9e59b247cd50 R12: ffff9e59b112f100
 R13: ffff9e59b112f108 R14: 0000000000000001 R15: ffff9e59ab12d0c0
 FS:  0000000000000000(0000) GS:ffff9e59b4700000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 000000006af92004 CR4: 00000000001606e0
 Call Trace:
  tcf_classify+0x58/0x120
  __dev_queue_xmit+0x40a/0x890
  ? ndisc_next_option+0x50/0x50
  ? ___neigh_create+0x4d5/0x680
  ? ip6_finish_output2+0x1b5/0x590
  ip6_finish_output2+0x1b5/0x590
  ? ip6_output+0x68/0x110
  ip6_output+0x68/0x110
  ? nf_hook.constprop.28+0x79/0xc0
  ndisc_send_skb+0x248/0x2e0
  ndisc_send_ns+0xf8/0x200
  ? addrconf_dad_work+0x389/0x4b0
  addrconf_dad_work+0x389/0x4b0
  ? __switch_to_asm+0x34/0x70
  ? process_one_work+0x195/0x380
  ? addrconf_dad_completed+0x370/0x370
  process_one_work+0x195/0x380
  worker_thread+0x30/0x390
  ? process_one_work+0x380/0x380
  kthread+0x113/0x130
  ? kthread_park+0x90/0x90
  ret_from_fork+0x35/0x40
 Modules linked in: act_simple veth ip6table_filter ip6_tables iptable_filter binfmt_misc crct10dif_pclmul crc32_pclmul ghash_clmulni_intel ext4 snd_hda_codec_generic snd_hda_intel snd_hda_codec snd_hwdep mbcache snd_hda_core jbd2 snd_seq snd_seq_device snd_pcm aesni_intel crypto_simd cryptd snd_timer glue_helper snd joydev virtio_balloon pcspkr 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 virtio_net ttm net_failover virtio_console virtio_blk failover drm crc32c_intel serio_raw floppy ata_piix libata virtio_pci virtio_ring virtio dm_mirror dm_region_hash dm_log dm_mod
 CR2: 0000000000000000

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

Fixes: db50514 ("net: sched: add termination action to allow goto chain")
Fixes: 97763dc ("net_sched: reject unknown tcfa_action values")
Signed-off-by: Davide Caratti <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: dcaratti

net/sched/act_simple.c

@@ -18,6 +18,7 @@
 #include <linux/rtnetlink.h>
 #include <net/netlink.h>
 #include <net/pkt_sched.h>
+#include <net/pkt_cls.h>
 
 #include <linux/tc_act/tc_defact.h>
 #include <net/tc_act/tc_defact.h>
@@ -60,14 +61,26 @@ static int alloc_defdata(struct tcf_defact *d, const struct nlattr *defdata)
 	return 0;
 }
 
-static void reset_policy(struct tcf_defact *d, const struct nlattr *defdata,
-			 struct tc_defact *p)
+static int reset_policy(struct tc_action *a, const struct nlattr *defdata,
+			struct tc_defact *p, struct tcf_proto *tp,
+			struct netlink_ext_ack *extack)
 {
+	struct tcf_chain *goto_ch = NULL;
+	struct tcf_defact *d;
+	int err;
+
+	err = tcf_action_check_ctrlact(p->action, tp, &goto_ch, extack);
+	if (err < 0)
+		return err;
+	d = to_defact(a);
 	spin_lock_bh(&d->tcf_lock);
-	d->tcf_action = p->action;
+	goto_ch = tcf_action_set_ctrlact(a, p->action, goto_ch);
 	memset(d->tcfd_defdata, 0, SIMP_MAX_DATA);
 	nla_strlcpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
 	spin_unlock_bh(&d->tcf_lock);
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+	return 0;
 }
 
 static const struct nla_policy simple_policy[TCA_DEF_MAX + 1] = {
@@ -82,6 +95,7 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 {
 	struct tc_action_net *tn = net_generic(net, simp_net_id);
 	struct nlattr *tb[TCA_DEF_MAX + 1];
+	struct tcf_chain *goto_ch = NULL;
 	struct tc_defact *parm;
 	struct tcf_defact *d;
 	bool exists = false;
@@ -122,27 +136,37 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 		}
 
 		d = to_defact(*a);
-		ret = alloc_defdata(d, tb[TCA_DEF_DATA]);
-		if (ret < 0) {
-			tcf_idr_release(*a, bind);
-			return ret;
-		}
-		d->tcf_action = parm->action;
+		err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch,
+					       extack);
+		if (err < 0)
+			goto release_idr;
+
+		err = alloc_defdata(d, tb[TCA_DEF_DATA]);
+		if (err < 0)
+			goto put_chain;
+
+		tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 		ret = ACT_P_CREATED;
 	} else {
-		d = to_defact(*a);
-
 		if (!ovr) {
-			tcf_idr_release(*a, bind);
-			return -EEXIST;
+			err = -EEXIST;
+			goto release_idr;
 		}
 
-		reset_policy(d, tb[TCA_DEF_DATA], parm);
+		err = reset_policy(*a, tb[TCA_DEF_DATA], parm, tp, extack);
+		if (err)
+			goto release_idr;
 	}
 
 	if (ret == ACT_P_CREATED)
 		tcf_idr_insert(tn, *a);
 	return ret;
+put_chain:
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+release_idr:
+	tcf_idr_release(*a, bind);
+	return err;
 }
 
 static int tcf_simp_dump(struct sk_buff *skb, struct tc_action *a,

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

@@ -126,5 +126,30 @@
         "teardown": [
             ""
         ]
+    },
+    {
+        "id": "b776",
+        "name": "Replace simple action with invalid goto chain control",
+        "category": [
+            "actions",
+            "simple"
+        ],
+        "setup": [
+            [
+                "$TC actions flush action simple",
+                0,
+                1,
+                255
+            ],
+            "$TC actions add action simple sdata \"hello\" pass index 90"
+        ],
+        "cmdUnderTest": "$TC actions replace action simple sdata \"world\" goto chain 42 index  90 cookie c1a0c1a0",
+        "expExitCode": "255",
+        "verifyCmd": "$TC actions list action simple",
+        "matchPattern": "action order [0-9]*: Simple <hello>.*index 90 ref",
+        "matchCount": "1",
+        "teardown": [
+            "$TC actions flush action simple"
+        ]
     }
 ]