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net/sched: act_connmark: 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 connmark pass index 90
 # tc actions replace action connmark \
 > goto chain 42 index 90 cookie c1a0c1a0
 # tc actions show action connmark

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: connmark zone 0 goto chain 42
          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 0 P4D 0
 Oops: 0000 [#1] SMP PTI
 CPU: 0 PID: 302 Comm: kworker/0:2 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:ffff9bea406c3ad0 EFLAGS: 00010246
 RAX: 000000002000002a RBX: ffff8c5dfc009f00 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: ffff9bea406c3a80 RDI: ffff8c5dfb9d6ec0
 RBP: ffff9bea406c3b70 R08: ffff8c5dfda222a0 R09: ffffffff90933c3c
 R10: 0000000000000000 R11: 0000000092793f7d R12: ffff8c5df48b3c00
 R13: ffff8c5df48b3c08 R14: 0000000000000001 R15: ffff8c5dfb9d6e40
 FS:  0000000000000000(0000) GS:ffff8c5dfda00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 0000000062e0e006 CR4: 00000000001606f0
 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_connmark nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 veth ip6table_filter ip6_tables iptable_filter binfmt_misc ext4 crct10dif_pclmul mbcache crc32_pclmul jbd2 snd_hda_codec_generic ghash_clmulni_intel snd_hda_intel snd_hda_codec snd_hwdep snd_hda_core snd_seq snd_seq_device snd_pcm aesni_intel snd_timer crypto_simd cryptd snd glue_helper 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 virtio_net net_failover syscopyarea virtio_blk failover virtio_console sysfillrect sysimgblt fb_sys_fops ttm drm ata_piix crc32c_intel serio_raw libata virtio_pci virtio_ring virtio floppy dm_mirror dm_region_hash dm_log dm_mod
 CR2: 0000000000000000

Validating the control action within tcf_connmark_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 fb433c6 commit 1b3615f
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Showing 2 changed files with 43 additions and 3 deletions.
21 changes: 18 additions & 3 deletions net/sched/act_connmark.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/act_api.h>
#include <net/pkt_cls.h>
#include <uapi/linux/tc_act/tc_connmark.h>
#include <net/tc_act/tc_connmark.h>

Expand Down Expand Up @@ -102,9 +103,10 @@ static int tcf_connmark_init(struct net *net, struct nlattr *nla,
{
struct tc_action_net *tn = net_generic(net, connmark_net_id);
struct nlattr *tb[TCA_CONNMARK_MAX + 1];
struct tcf_chain *goto_ch = NULL;
struct tcf_connmark_info *ci;
struct tc_connmark *parm;
int ret = 0;
int ret = 0, err;

if (!nla)
return -EINVAL;
Expand All @@ -129,7 +131,11 @@ static int tcf_connmark_init(struct net *net, struct nlattr *nla,
}

ci = to_connmark(*a);
ci->tcf_action = parm->action;
err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch,
extack);
if (err < 0)
goto release_idr;
tcf_action_set_ctrlact(*a, parm->action, goto_ch);
ci->net = net;
ci->zone = parm->zone;

Expand All @@ -143,15 +149,24 @@ static int tcf_connmark_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;
/* replacing action and zone */
spin_lock_bh(&ci->tcf_lock);
ci->tcf_action = parm->action;
goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
ci->zone = parm->zone;
spin_unlock_bh(&ci->tcf_lock);
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
ret = 0;
}

return ret;
release_idr:
tcf_idr_release(*a, bind);
return err;
}

static inline int tcf_connmark_dump(struct sk_buff *skb, struct tc_action *a,
Expand Down
25 changes: 25 additions & 0 deletions tools/testing/selftests/tc-testing/tc-tests/actions/connmark.json
View file
Original file line number Diff line number Diff line change
Expand Up @@ -287,5 +287,30 @@
"teardown": [
"$TC actions flush action connmark"
]
},
{
"id": "c506",
"name": "Replace connmark with invalid goto chain control",
"category": [
"actions",
"connmark"
],
"setup": [
[
"$TC actions flush action connmark",
0,
1,
255
],
"$TC actions add action connmark pass index 90"
],
"cmdUnderTest": "$TC actions replace action connmark goto chain 42 index 90 cookie c1a0c1a0",
"expExitCode": "255",
"verifyCmd": "$TC actions get action connmark index 90",
"matchPattern": "action order [0-9]+: connmark zone 0 pass.*index 90 ref",
"matchCount": "1",
"teardown": [
"$TC actions flush action connmark"
]
}
]

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