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

 # tc filter add dev crash0 egress matchall \
 > action pedit ex munge ip ttl set 10 pass index 90
 # tc actions replace action pedit \
 > ex munge ip ttl set 10 goto chain 42 index 90 cookie c1a0c1a0
 # tc actions show action pedit

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:  pedit action goto chain 42 keys 1
          index 90 ref 2 bind 1
          key #0  at ipv4+8: val 0a000000 mask 00ffffff
         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 0 P4D 0
 Oops: 0000 [#1] SMP PTI
 CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.0.0-rc4.gotochain_crash+ torvalds#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:ffff94a73db03be0 EFLAGS: 00010246
 RAX: 000000002000002a RBX: ffff94a6ee4c0700 RCX: 000000000000000a
 RDX: 0000000000000000 RSI: ffff94a6ed22c800 RDI: 0000000000000000
 RBP: ffff94a73db03c80 R08: ffff94a7386fa4c8 R09: ffff94a73229ea20
 R10: 0000000000000000 R11: 0000000000000000 R12: ffff94a6ed22cb00
 R13: ffff94a6ed22cb08 R14: 0000000000000001 R15: ffff94a6ed22c800
 FS:  0000000000000000(0000) GS:ffff94a73db00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 000000007120e002 CR4: 00000000001606e0
 Call Trace:
  <IRQ>
  tcf_classify+0x58/0x120
  __dev_queue_xmit+0x40a/0x890
  ? ip6_finish_output2+0x369/0x590
  ip6_finish_output2+0x369/0x590
  ? ip6_output+0x68/0x110
  ip6_output+0x68/0x110
  ? nf_hook.constprop.35+0x79/0xc0
  mld_sendpack+0x16f/0x220
  mld_ifc_timer_expire+0x195/0x2c0
  ? igmp6_timer_handler+0x70/0x70
  call_timer_fn+0x2b/0x130
  run_timer_softirq+0x3e8/0x440
  ? tick_sched_timer+0x37/0x70
  __do_softirq+0xe3/0x2f5
  irq_exit+0xf0/0x100
  smp_apic_timer_interrupt+0x6c/0x130
  apic_timer_interrupt+0xf/0x20
  </IRQ>
 RIP: 0010:native_safe_halt+0x2/0x10
 Code: 4e ff ff ff 7f f3 c3 65 48 8b 04 25 00 5c 01 00 f0 80 48 02 20 48 8b 00 a8 08 74 8b eb c1 90 90 90 90 90 90 90 90 90 90 fb f4 <c3> 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 f4 c3 90 90 90 90 90 90
 RSP: 0018:ffffab1740387eb8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
 RAX: ffffffffb18184f0 RBX: 0000000000000002 RCX: 0000000000000001
 RDX: 0000000000000001 RSI: 0000000000000087 RDI: 0000000000000002
 RBP: 0000000000000002 R08: 000f168fa695f9a9 R09: 0000000000000020
 R10: 0000000000000004 R11: 0000000000000000 R12: 0000000000000000
 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
  ? __sched_text_end+0x1/0x1
  default_idle+0x1c/0x140
  do_idle+0x1c4/0x280
  cpu_startup_entry+0x19/0x20
  start_secondary+0x1a7/0x200
  secondary_startup_64+0xa4/0xb0
 Modules linked in: act_pedit veth ip6table_filter ip6_tables iptable_filter binfmt_misc ext4 mbcache jbd2 crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd_hda_codec_generic snd_hda_intel snd_hda_codec snd_hwdep aesni_intel snd_hda_core crypto_simd snd_seq cryptd glue_helper snd_seq_device snd_pcm joydev snd_timer pcspkr virtio_balloon snd soundcore i2c_piix4 nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs qxl ata_generic pata_acpi drm_kms_helper virtio_net net_failover syscopyarea sysfillrect sysimgblt failover virtio_blk fb_sys_fops virtio_console ttm drm crc32c_intel serio_raw ata_piix virtio_pci libata virtio_ring virtio floppy dm_mirror dm_region_hash dm_log dm_mod
 CR2: 0000000000000000

Validating the control action within tcf_pedit_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 @davem330
dcaratti authored and davem330 committed Mar 21, 2019
1 parent 1e45d04 commit 6ac86ca
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Showing 2 changed files with 65 additions and 2 deletions.
16 changes: 14 additions & 2 deletions net/sched/act_pedit.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@
#include <linux/tc_act/tc_pedit.h>
#include <net/tc_act/tc_pedit.h>
#include <uapi/linux/tc_act/tc_pedit.h>
#include <net/pkt_cls.h>

static unsigned int pedit_net_id;
static struct tc_action_ops act_pedit_ops;
Expand Down Expand Up @@ -142,6 +143,7 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
{
struct tc_action_net *tn = net_generic(net, pedit_net_id);
struct nlattr *tb[TCA_PEDIT_MAX + 1];
struct tcf_chain *goto_ch = NULL;
struct tc_pedit_key *keys = NULL;
struct tcf_pedit_key_ex *keys_ex;
struct tc_pedit *parm;
Expand Down Expand Up @@ -205,6 +207,11 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
goto out_free;
}

err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
if (err < 0) {
ret = err;
goto out_release;
}
p = to_pedit(*a);
spin_lock_bh(&p->tcf_lock);

Expand All @@ -214,7 +221,7 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
if (!keys) {
spin_unlock_bh(&p->tcf_lock);
ret = -ENOMEM;
goto out_release;
goto put_chain;
}
kfree(p->tcfp_keys);
p->tcfp_keys = keys;
Expand All @@ -223,16 +230,21 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
memcpy(p->tcfp_keys, parm->keys, ksize);

p->tcfp_flags = parm->flags;
p->tcf_action = parm->action;
goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);

kfree(p->tcfp_keys_ex);
p->tcfp_keys_ex = keys_ex;

spin_unlock_bh(&p->tcf_lock);
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
if (ret == ACT_P_CREATED)
tcf_idr_insert(tn, *a);
return ret;

put_chain:
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
out_release:
tcf_idr_release(*a, bind);
out_free:
Expand Down
51 changes: 51 additions & 0 deletions tools/testing/selftests/tc-testing/tc-tests/actions/pedit.json
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,51 @@
[
{
"id": "319a",
"name": "Add pedit action that mangles IP TTL",
"category": [
"actions",
"pedit"
],
"setup": [
[
"$TC actions flush action pedit",
0,
1,
255
]
],
"cmdUnderTest": "$TC actions add action pedit ex munge ip ttl set 10",
"expExitCode": "0",
"verifyCmd": "$TC actions ls action pedit",
"matchPattern": "action order [0-9]+: pedit action pass keys 1.*index 1 ref.*key #0 at ipv4\\+8: val 0a000000 mask 00ffffff",
"matchCount": "1",
"teardown": [
"$TC actions flush action pedit"
]
},
{
"id": "7e67",
"name": "Replace pedit action with invalid goto chain",
"category": [
"actions",
"pedit"
],
"setup": [
[
"$TC actions flush action pedit",
0,
1,
255
],
"$TC actions add action pedit ex munge ip ttl set 10 pass index 90"
],
"cmdUnderTest": "$TC actions replace action pedit ex munge ip ttl set 10 goto chain 42 index 90 cookie c1a0c1a0",
"expExitCode": "255",
"verifyCmd": "$TC actions ls action pedit",
"matchPattern": "action order [0-9]+: pedit action pass keys 1.*index 90 ref.*key #0 at ipv4\\+8: val 0a000000 mask 00ffffff",
"matchCount": "1",
"teardown": [
"$TC actions flush action pedit"
]
}
]

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