CVE-2021-46936 (GCVE-0-2021-46936)

Vulnerability from cvelistv5 – Published: 2024-02-27 09:44 – Updated: 2025-05-04 07:00
VLAI?
Title
net: fix use-after-free in tw_timer_handler
Summary
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
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 , < 15579e1301f856ad9385d720c9267c11032a5022 (git)
Affected: 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 , < e73164e89d1be561228a4534e1091369ee4ba41a (git)
Affected: 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 , < 5c2fe20ad37ff56070ae0acb34152333976929b4 (git)
Affected: 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 , < a8e1944b44f94f5c5f530e434c5eaee787254566 (git)
Affected: 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 , < fe5838c22b986c1190f1dce9aa09bf6a491c1a69 (git)
Affected: 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 , < 2386e81a1d277f540e1285565c9d41d531bb69d4 (git)
Affected: 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 , < 08eacbd141e2495d2fcdde84358a06c4f95cbb13 (git)
Affected: 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 , < e22e45fc9e41bf9fcc1e92cfb78eb92786728ef0 (git)
Create a notification for this product.
    Linux Linux Affected: 2.6.27
Unaffected: 0 , < 2.6.27 (semver)
Unaffected: 4.4.298 , ≤ 4.4.* (semver)
Unaffected: 4.9.296 , ≤ 4.9.* (semver)
Unaffected: 4.14.261 , ≤ 4.14.* (semver)
Unaffected: 4.19.224 , ≤ 4.19.* (semver)
Unaffected: 5.4.170 , ≤ 5.4.* (semver)
Unaffected: 5.10.90 , ≤ 5.10.* (semver)
Unaffected: 5.15.13 , ≤ 5.15.* (semver)
Unaffected: 5.16 , ≤ * (original_commit_for_fix)
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{\"url\": \"https://git.kernel.org/stable/c/5c2fe20ad37ff56070ae0acb34152333976929b4\"}, {\"url\": \"https://git.kernel.org/stable/c/a8e1944b44f94f5c5f530e434c5eaee787254566\"}, {\"url\": \"https://git.kernel.org/stable/c/fe5838c22b986c1190f1dce9aa09bf6a491c1a69\"}, {\"url\": \"https://git.kernel.org/stable/c/2386e81a1d277f540e1285565c9d41d531bb69d4\"}, {\"url\": \"https://git.kernel.org/stable/c/08eacbd141e2495d2fcdde84358a06c4f95cbb13\"}, {\"url\": \"https://git.kernel.org/stable/c/e22e45fc9e41bf9fcc1e92cfb78eb92786728ef0\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: fix use-after-free in tw_timer_handler\\n\\nA real world panic issue was found as follow in Linux 5.4.\\n\\n    BUG: unable to handle page fault for address: ffffde49a863de28\\n    PGD 7e6fe62067 P4D 7e6fe62067 PUD 7e6fe63067 PMD f51e064067 PTE 0\\n    RIP: 0010:tw_timer_handler+0x20/0x40\\n    Call Trace:\\n     \u003cIRQ\u003e\\n     call_timer_fn+0x2b/0x120\\n     run_timer_softirq+0x1ef/0x450\\n     __do_softirq+0x10d/0x2b8\\n     irq_exit+0xc7/0xd0\\n     smp_apic_timer_interrupt+0x68/0x120\\n     apic_timer_interrupt+0xf/0x20\\n\\nThis issue was also reported since 2017 in the thread [1],\\nunfortunately, the issue was still can be reproduced after fixing\\nDCCP.\\n\\nThe ipv4_mib_exit_net is called before tcp_sk_exit_batch when a net\\nnamespace is destroyed since tcp_sk_ops is registered befrore\\nipv4_mib_ops, which means tcp_sk_ops is in the front of ipv4_mib_ops\\nin the list of pernet_list. There will be a use-after-free on\\nnet-\u003emib.net_statistics in tw_timer_handler after ipv4_mib_exit_net\\nif there are some inflight time-wait timers.\\n\\nThis bug is not introduced by commit f2bf415cfed7 (\\\"mib: add net to\\nNET_ADD_STATS_BH\\\") since the net_statistics is a global variable\\ninstead of dynamic allocation and freeing. Actually, commit\\n61a7e26028b9 (\\\"mib: put net statistics on struct net\\\") introduces\\nthe bug since it put net statistics on struct net and free it when\\nnet namespace is destroyed.\\n\\nMoving init_ipv4_mibs() to the front of tcp_init() to fix this bug\\nand replace pr_crit() with panic() since continuing is meaningless\\nwhen init_ipv4_mibs() fails.\\n\\n[1] https://groups.google.com/g/syzkaller/c/p1tn-_Kc6l4/m/smuL_FMAAgAJ?pli=1\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.4.298\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.9.296\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.14.261\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.19.224\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.170\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.90\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.13\", \"versionStartIncluding\": \"2.6.27\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.16\", \"versionStartIncluding\": \"2.6.27\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2025-05-04T07:00:40.694Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-46936\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2025-05-04T07:00:40.694Z\", \"dateReserved\": \"2024-02-25T13:45:52.720Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-02-27T09:44:02.758Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}


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Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.