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LinuxCVE-2021-46936

HistoryFeb 27, 2024 - 10:15 a.m.

CVE-2021-46936

2024-02-2710:15:08

CWE-416

Linux

web.nvd.nist.gov

596

linux kernel

net

use-after-free

tw_timer_handler

cve-2021-46936

vulnerability

security

nvd

linux 5.4

panic issue

CVSS3

7.8

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

AI Score

6.3

Confidence

Low

EPSS

Percentile

5.1%

JSON

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

net: fix use-after-free in tw_timer_handler

A real world panic issue was found as follow in Linux 5.4.

BUG: unable to handle page fault for address: ffffde49a863de28
PGD 7e6fe62067 P4D 7e6fe62067 PUD 7e6fe63067 PMD f51e064067 PTE 0
RIP: 0010:tw_timer_handler+0x20/0x40
Call Trace:
 &lt;IRQ&gt;
 call_timer_fn+0x2b/0x120
 run_timer_softirq+0x1ef/0x450
 __do_softirq+0x10d/0x2b8
 irq_exit+0xc7/0xd0
 smp_apic_timer_interrupt+0x68/0x120
 apic_timer_interrupt+0xf/0x20

This issue was also reported since 2017 in the thread [1],
unfortunately, the issue was still can be reproduced after fixing
DCCP.

The ipv4_mib_exit_net is called before tcp_sk_exit_batch when a net
namespace is destroyed since tcp_sk_ops is registered befrore
ipv4_mib_ops, which means tcp_sk_ops is in the front of ipv4_mib_ops
in the list of pernet_list. There will be a use-after-free on
net->mib.net_statistics in tw_timer_handler after ipv4_mib_exit_net
if there are some inflight time-wait timers.

This bug is not introduced by commit f2bf415cfed7 (“mib: add net to
NET_ADD_STATS_BH”) since the net_statistics is a global variable
instead of dynamic allocation and freeing. Actually, commit
61a7e26028b9 (“mib: put net statistics on struct net”) introduces
the bug since it put net statistics on struct net and free it when
net namespace is destroyed.

Moving init_ipv4_mibs() to the front of tcp_init() to fix this bug
and replace pr_crit() with panic() since continuing is meaningless
when init_ipv4_mibs() fails.

[1] https://groups.google.com/g/syzkaller/c/p1tn-_Kc6l4/m/smuL_FMAAgAJ?pli=1

Affected configurations

Nvd

Vulners

Node

linuxlinux_kernelRange2.6.27–4.4.298

linuxlinux_kernelRange4.5.0–4.9.296

linuxlinux_kernelRange4.10.0–4.14.261

linuxlinux_kernelRange4.15.0–4.19.224

linuxlinux_kernelRange4.20.0–5.4.170

linuxlinux_kernelRange5.5.0–5.10.90

linuxlinux_kernelRange5.11.0–5.15.13

VendorProductVersionCPE
linuxlinux_kernel*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

Vendor	Product	Version	CPE
linux	linux_kernel	*	cpe:2.3:o:linux:linux_kernel::::::::

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "net/ipv4/af_inet.c"
    ],
    "versions": [
      {
        "version": "61a7e26028b9",
        "lessThan": "15579e1301f8",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "61a7e26028b9",
        "lessThan": "e73164e89d1b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "61a7e26028b9",
        "lessThan": "5c2fe20ad37f",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "61a7e26028b9",
        "lessThan": "a8e1944b44f9",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "61a7e26028b9",
        "lessThan": "fe5838c22b98",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "61a7e26028b9",
        "lessThan": "2386e81a1d27",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "61a7e26028b9",
        "lessThan": "08eacbd141e2",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "61a7e26028b9",
        "lessThan": "e22e45fc9e41",
        "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/ipv4/af_inet.c"
    ],
    "versions": [
      {
        "version": "2.6.27",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "2.6.27",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.4.298",
        "lessThanOrEqual": "4.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.9.296",
        "lessThanOrEqual": "4.9.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.14.261",
        "lessThanOrEqual": "4.14.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.19.224",
        "lessThanOrEqual": "4.19.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.170",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.90",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.13",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.16",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]