Lucene search

K
cvelistLinuxCVELIST:CVE-2021-46955
HistoryFeb 27, 2024 - 6:46 p.m.

CVE-2021-46955 openvswitch: fix stack OOB read while fragmenting IPv4 packets

2024-02-2718:46:57
Linux
www.cve.org
2
openvswitch
vulnerability
stack
out-of-bounds
ipv4
packets
kernel
kasan
linux
fragmentation
fix
struct
dst_entry
rtable

AI Score

7.6

Confidence

High

EPSS

0

Percentile

13.0%

In the Linux kernel, the following vulnerability has been resolved:

openvswitch: fix stack OOB read while fragmenting IPv4 packets

running openvswitch on kernels built with KASAN, it’s possible to see the
following splat while testing fragmentation of IPv4 packets:

BUG: KASAN: stack-out-of-bounds in ip_do_fragment+0x1b03/0x1f60
Read of size 1 at addr ffff888112fc713c by task handler2/1367

CPU: 0 PID: 1367 Comm: handler2 Not tainted 5.12.0-rc6+ #418
Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
Call Trace:
dump_stack+0x92/0xc1
print_address_description.constprop.7+0x1a/0x150
kasan_report.cold.13+0x7f/0x111
ip_do_fragment+0x1b03/0x1f60
ovs_fragment+0x5bf/0x840 [openvswitch]
do_execute_actions+0x1bd5/0x2400 [openvswitch]
ovs_execute_actions+0xc8/0x3d0 [openvswitch]
ovs_packet_cmd_execute+0xa39/0x1150 [openvswitch]
genl_family_rcv_msg_doit.isra.15+0x227/0x2d0
genl_rcv_msg+0x287/0x490
netlink_rcv_skb+0x120/0x380
genl_rcv+0x24/0x40
netlink_unicast+0x439/0x630
netlink_sendmsg+0x719/0xbf0
sock_sendmsg+0xe2/0x110
____sys_sendmsg+0x5ba/0x890
___sys_sendmsg+0xe9/0x160
__sys_sendmsg+0xd3/0x170
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f957079db07
Code: c3 66 90 41 54 41 89 d4 55 48 89 f5 53 89 fb 48 83 ec 10 e8 eb ec ff ff 44 89 e2 48 89 ee 89 df 41 89 c0 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 48 89 44 24 08 e8 24 ed ff ff 48
RSP: 002b:00007f956ce35a50 EFLAGS: 00000293 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000019 RCX: 00007f957079db07
RDX: 0000000000000000 RSI: 00007f956ce35ae0 RDI: 0000000000000019
RBP: 00007f956ce35ae0 R08: 0000000000000000 R09: 00007f9558006730
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 00007f956ce37308 R14: 00007f956ce35f80 R15: 00007f956ce35ae0

The buggy address belongs to the page:
page:00000000af2a1d93 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112fc7
flags: 0x17ffffc0000000()
raw: 0017ffffc0000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

addr ffff888112fc713c is located in stack of task handler2/1367 at offset 180 in frame:
ovs_fragment+0x0/0x840 [openvswitch]

this frame has 2 objects:
[32, 144) ‘ovs_dst’
[192, 424) ‘ovs_rt’

Memory state around the buggy address:
ffff888112fc7000: f3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888112fc7080: 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00 00 00 00
>ffff888112fc7100: 00 00 00 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00
^
ffff888112fc7180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888112fc7200: 00 00 00 00 00 00 f2 f2 f2 00 00 00 00 00 00 00

for IPv4 packets, ovs_fragment() uses a temporary struct dst_entry. Then,
in the following call graph:

ip_do_fragment()
ip_skb_dst_mtu()
ip_dst_mtu_maybe_forward()
ip_mtu_locked()

the pointer to struct dst_entry is used as pointer to struct rtable: this
turns the access to struct members like rt_mtu_locked into an OOB read in
the stack. Fix this changing the temporary variable used for IPv4 packets
in ovs_fragment(), similarly to what is done for IPv6 few lines below.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "net/openvswitch/actions.c"
    ],
    "versions": [
      {
        "version": "119bbaa6795a",
        "lessThan": "b1d7280f9ba1",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "d543907a4730",
        "lessThan": "23e17ec1a5eb",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "8387fbac8e18",
        "lessThan": "5a52fa8ad45b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "d52e5a7e7ca4",
        "lessThan": "df9e900de246",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "d52e5a7e7ca4",
        "lessThan": "490ad0a23904",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "d52e5a7e7ca4",
        "lessThan": "a1478374b0bd",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "d52e5a7e7ca4",
        "lessThan": "d841d3cf5297",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "d52e5a7e7ca4",
        "lessThan": "b3502b04e84a",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "d52e5a7e7ca4",
        "lessThan": "7c0ea5930c1c",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "net/openvswitch/actions.c"
    ],
    "versions": [
      {
        "version": "4.16",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "4.16",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.4.269",
        "lessThanOrEqual": "4.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.9.269",
        "lessThanOrEqual": "4.9.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.14.233",
        "lessThanOrEqual": "4.14.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.19.191",
        "lessThanOrEqual": "4.19.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.118",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.36",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.11.20",
        "lessThanOrEqual": "5.11.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.12.3",
        "lessThanOrEqual": "5.12.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.13",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]

AI Score

7.6

Confidence

High

EPSS

0

Percentile

13.0%