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net/sched: act_ife: validate the control action inside init()
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the following script:

 # tc qdisc add dev crash0 clsact
 # tc filter add dev crash0 egress matchall \
 > action ife encode allow mark pass index 90
 # tc actions replace action ife \
 > encode allow mark goto chain 42 index 90 cookie c1a0c1a0
 # tc action show action ife

had the following output:

 IFE type 0xED3E
 IFE type 0xED3E
 Error: Failed to init TC action chain.
 We have an error talking to the kernel
 total acts 1

         action order 0: ife encode action goto chain 42 type 0XED3E
         allow mark
          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 800000007b4e7067 P4D 800000007b4e7067 PUD 7b4e6067 PMD 0
 Oops: 0000 [#1] SMP PTI
 CPU: 2 PID: 164 Comm: kworker/2:1 Not tainted 5.0.0-rc4.gotochain_crash+ torvalds#533
 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:ffffa6a7c0553ad0 EFLAGS: 00010246
 RAX: 000000002000002a RBX: ffff9796ee1bbd00 RCX: 0000000000000001
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
 RBP: ffffa6a7c0553b70 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: ffff9797385bb038 R12: ffff9796ead9d700
 R13: ffff9796ead9d708 R14: 0000000000000001 R15: ffff9796ead9d800
 FS:  0000000000000000(0000) GS:ffff97973db00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 000000007c41e006 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_gact act_meta_mark act_ife dummy veth ip6table_filter ip6_tables iptable_filter binfmt_misc snd_hda_codec_generic ext4 snd_hda_intel snd_hda_codec crct10dif_pclmul mbcache crc32_pclmul jbd2 snd_hwdep snd_hda_core ghash_clmulni_intel snd_seq snd_seq_device snd_pcm snd_timer aesni_intel crypto_simd snd cryptd glue_helper virtio_balloon joydev pcspkr soundcore i2c_piix4 nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs ata_generic pata_acpi qxl virtio_net drm_kms_helper virtio_blk net_failover syscopyarea failover sysfillrect virtio_console sysimgblt fb_sys_fops ttm drm crc32c_intel serio_raw ata_piix virtio_pci virtio_ring libata virtio floppy dm_mirror dm_region_hash dm_log dm_mod [last unloaded: act_ife]
 CR2: 0000000000000000

Validating the control action within tcf_ife_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 <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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@dcaratti
dcaratti authored and Chris Mi committed Dec 18, 2020
1 parent 258ac6e commit 195244d
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Showing 2 changed files with 45 additions and 13 deletions.
33 changes: 20 additions & 13 deletions net/sched/act_ife.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@
#include <net/net_namespace.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#include <uapi/linux/tc_act/tc_ife.h>
#include <net/tc_act/tc_ife.h>
#include <linux/etherdevice.h>
Expand Down Expand Up @@ -474,6 +475,7 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
struct tc_action_net *tn = net_generic(net, ife_net_id);
struct nlattr *tb[TCA_IFE_MAX + 1];
struct nlattr *tb2[IFE_META_MAX + 1];
struct tcf_chain *goto_ch = NULL;
struct tcf_ife_params *p;
struct tcf_ife_info *ife;
u16 ife_type = ETH_P_IFE;
Expand Down Expand Up @@ -531,6 +533,10 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
}

ife = to_ife(*a);
err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
if (err < 0)
goto release_idr;

p->flags = parm->flags;

if (parm->flags & IFE_ENCODE) {
Expand Down Expand Up @@ -563,13 +569,8 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
if (tb[TCA_IFE_METALST]) {
err = nla_parse_nested(tb2, IFE_META_MAX, tb[TCA_IFE_METALST],
NULL, NULL);
if (err) {
metadata_parse_err:
tcf_idr_release(*a, bind);
kfree(p);
return err;
}

if (err)
goto metadata_parse_err;
err = populate_metalist(ife, tb2, exists, rtnl_held);
if (err)
goto metadata_parse_err;
Expand All @@ -581,28 +582,34 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
* going to bail out
*/
err = use_all_metadata(ife, exists);
if (err) {
tcf_idr_release(*a, bind);
kfree(p);
return err;
}
if (err)
goto metadata_parse_err;
}

if (exists)
spin_lock_bh(&ife->tcf_lock);
ife->tcf_action = parm->action;
/* protected by tcf_lock when modifying existing action */
goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
rcu_swap_protected(ife->params, p, 1);

if (exists)
spin_unlock_bh(&ife->tcf_lock);
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
if (p)
kfree_rcu(p, rcu);

if (ret == ACT_P_CREATED)
tcf_idr_insert(tn, *a);

return ret;
metadata_parse_err:
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
release_idr:
kfree(p);
tcf_idr_release(*a, bind);
return err;
}

static int tcf_ife_dump(struct sk_buff *skb, struct tc_action *a, int bind,
Expand Down
25 changes: 25 additions & 0 deletions tools/testing/selftests/tc-testing/tc-tests/actions/ife.json
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1060,5 +1060,30 @@
"matchPattern": "action order [0-9]*: ife encode action pipe.*allow prio.*index 4",
"matchCount": "0",
"teardown": []
},
{
"id": "a0e2",
"name": "Replace ife encode action with invalid goto chain control",
"category": [
"actions",
"ife"
],
"setup": [
[
"$TC actions flush action ife",
0,
1,
255
],
"$TC actions add action ife encode allow mark pass index 90"
],
"cmdUnderTest": "$TC actions replace action ife encode allow mark goto chain 42 index 90 cookie c1a0c1a0",
"expExitCode": "255",
"verifyCmd": "$TC actions get action ife index 90",
"matchPattern": "action order [0-9]*: ife encode action pass.*type 0[xX]ED3E .*allow mark.*index 90 ref",
"matchCount": "1",
"teardown": [
"$TC actions flush action ife"
]
}
]

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