CVE-2021-46936

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Source
https://cve.org/CVERecord?id=CVE-2021-46936
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-46936.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2021-46936
Downstream
Related
Published
2024-02-27T10:15:08Z
Modified
2026-03-15T22:42:41Z
Severity
  • 7.8 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
Summary
[none]
Details

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:
 <IRQ>
 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

References

Affected packages

Git /

Affected ranges

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-46936.json"
unresolved_ranges 
[
    {
        "events": [
            {
                "introduced": "2.6.27"
            },
            {
                "fixed": "4.4.298"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "4.5.0"
            },
            {
                "fixed": "4.9.296"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "4.10.0"
            },
            {
                "fixed": "4.14.261"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "4.15.0"
            },
            {
                "fixed": "4.19.224"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "4.20.0"
            },
            {
                "fixed": "5.4.170"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "5.5.0"
            },
            {
                "fixed": "5.10.90"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "5.11.0"
            },
            {
                "fixed": "5.15.13"
            }
        ]
    }
]