ghsa-hm85-hr96-4gwf
Vulnerability from github
Published
2024-08-21 09:31
Modified
2024-08-29 03:30
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Details

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

sched/core: Fix use-after-free bug in dup_user_cpus_ptr()

Since commit 07ec77a1d4e8 ("sched: Allow task CPU affinity to be restricted on asymmetric systems"), the setting and clearing of user_cpus_ptr are done under pi_lock for arm64 architecture. However, dup_user_cpus_ptr() accesses user_cpus_ptr without any lock protection. Since sched_setaffinity() can be invoked from another process, the process being modified may be undergoing fork() at the same time. When racing with the clearing of user_cpus_ptr in __set_cpus_allowed_ptr_locked(), it can lead to user-after-free and possibly double-free in arm64 kernel.

Commit 8f9ea86fdf99 ("sched: Always preserve the user requested cpumask") fixes this problem as user_cpus_ptr, once set, will never be cleared in a task's lifetime. However, this bug was re-introduced in commit 851a723e45d1 ("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()") which allows the clearing of user_cpus_ptr in do_set_cpus_allowed(). This time, it will affect all arches.

Fix this bug by always clearing the user_cpus_ptr of the newly cloned/forked task before the copying process starts and check the user_cpus_ptr state of the source task under pi_lock.

Note to stable, this patch won't be applicable to stable releases. Just copy the new dup_user_cpus_ptr() function over.

Show details on source website

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{
   affected: [],
   aliases: [
      "CVE-2022-48892",
   ],
   database_specific: {
      cwe_ids: [
         "CWE-415",
      ],
      github_reviewed: false,
      github_reviewed_at: null,
      nvd_published_at: "2024-08-21T07:15:05Z",
      severity: "HIGH",
   },
   details: "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/core: Fix use-after-free bug in dup_user_cpus_ptr()\n\nSince commit 07ec77a1d4e8 (\"sched: Allow task CPU affinity to be\nrestricted on asymmetric systems\"), the setting and clearing of\nuser_cpus_ptr are done under pi_lock for arm64 architecture. However,\ndup_user_cpus_ptr() accesses user_cpus_ptr without any lock\nprotection. Since sched_setaffinity() can be invoked from another\nprocess, the process being modified may be undergoing fork() at\nthe same time.  When racing with the clearing of user_cpus_ptr in\n__set_cpus_allowed_ptr_locked(), it can lead to user-after-free and\npossibly double-free in arm64 kernel.\n\nCommit 8f9ea86fdf99 (\"sched: Always preserve the user requested\ncpumask\") fixes this problem as user_cpus_ptr, once set, will never\nbe cleared in a task's lifetime. However, this bug was re-introduced\nin commit 851a723e45d1 (\"sched: Always clear user_cpus_ptr in\ndo_set_cpus_allowed()\") which allows the clearing of user_cpus_ptr in\ndo_set_cpus_allowed(). This time, it will affect all arches.\n\nFix this bug by always clearing the user_cpus_ptr of the newly\ncloned/forked task before the copying process starts and check the\nuser_cpus_ptr state of the source task under pi_lock.\n\nNote to stable, this patch won't be applicable to stable releases.\nJust copy the new dup_user_cpus_ptr() function over.",
   id: "GHSA-hm85-hr96-4gwf",
   modified: "2024-08-29T03:30:49Z",
   published: "2024-08-21T09:31:32Z",
   references: [
      {
         type: "ADVISORY",
         url: "https://nvd.nist.gov/vuln/detail/CVE-2022-48892",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/7b5cc7fd1789ea5dbb942c9f8207b076d365badc",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/87ca4f9efbd7cc649ff43b87970888f2812945b8",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/b22faa21b6230d5eccd233e1b7e0026a5002b287",
      },
   ],
   schema_version: "1.4.0",
   severity: [
      {
         score: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
         type: "CVSS_V3",
      },
   ],
}


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