ghsa-8h6j-vxpr-4ff5
Vulnerability from github
Published
2024-02-27 21:31
Modified
2024-04-10 21:30
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Details

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

tracing: Restructure trace_clock_global() to never block

It was reported that a fix to the ring buffer recursion detection would cause a hung machine when performing suspend / resume testing. The following backtrace was extracted from debugging that case:

Call Trace: trace_clock_global+0x91/0xa0 __rb_reserve_next+0x237/0x460 ring_buffer_lock_reserve+0x12a/0x3f0 trace_buffer_lock_reserve+0x10/0x50 __trace_graph_return+0x1f/0x80 trace_graph_return+0xb7/0xf0 ? trace_clock_global+0x91/0xa0 ftrace_return_to_handler+0x8b/0xf0 ? pv_hash+0xa0/0xa0 return_to_handler+0x15/0x30 ? ftrace_graph_caller+0xa0/0xa0 ? trace_clock_global+0x91/0xa0 ? __rb_reserve_next+0x237/0x460 ? ring_buffer_lock_reserve+0x12a/0x3f0 ? trace_event_buffer_lock_reserve+0x3c/0x120 ? trace_event_buffer_reserve+0x6b/0xc0 ? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0 ? dpm_run_callback+0x3b/0xc0 ? pm_ops_is_empty+0x50/0x50 ? platform_get_irq_byname_optional+0x90/0x90 ? trace_device_pm_callback_start+0x82/0xd0 ? dpm_run_callback+0x49/0xc0

With the following RIP:

RIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200

Since the fix to the recursion detection would allow a single recursion to happen while tracing, this lead to the trace_clock_global() taking a spin lock and then trying to take it again:

ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath() { / lock taken / (something else gets traced by function graph tracer) ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath() { / DEAD LOCK! /

Tracing should never block, as it can lead to strange lockups like the above.

Restructure the trace_clock_global() code to instead of simply taking a lock to update the recorded "prev_time" simply use it, as two events happening on two different CPUs that calls this at the same time, really doesn't matter which one goes first. Use a trylock to grab the lock for updating the prev_time, and if it fails, simply try again the next time. If it failed to be taken, that means something else is already updating it.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212761

Show details on source website

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{
  "affected": [],
  "aliases": [
    "CVE-2021-46939"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-662"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-02-27T19:04:05Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Restructure trace_clock_global() to never block\n\nIt was reported that a fix to the ring buffer recursion detection would\ncause a hung machine when performing suspend / resume testing. The\nfollowing backtrace was extracted from debugging that case:\n\nCall Trace:\n trace_clock_global+0x91/0xa0\n __rb_reserve_next+0x237/0x460\n ring_buffer_lock_reserve+0x12a/0x3f0\n trace_buffer_lock_reserve+0x10/0x50\n __trace_graph_return+0x1f/0x80\n trace_graph_return+0xb7/0xf0\n ? trace_clock_global+0x91/0xa0\n ftrace_return_to_handler+0x8b/0xf0\n ? pv_hash+0xa0/0xa0\n return_to_handler+0x15/0x30\n ? ftrace_graph_caller+0xa0/0xa0\n ? trace_clock_global+0x91/0xa0\n ? __rb_reserve_next+0x237/0x460\n ? ring_buffer_lock_reserve+0x12a/0x3f0\n ? trace_event_buffer_lock_reserve+0x3c/0x120\n ? trace_event_buffer_reserve+0x6b/0xc0\n ? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0\n ? dpm_run_callback+0x3b/0xc0\n ? pm_ops_is_empty+0x50/0x50\n ? platform_get_irq_byname_optional+0x90/0x90\n ? trace_device_pm_callback_start+0x82/0xd0\n ? dpm_run_callback+0x49/0xc0\n\nWith the following RIP:\n\nRIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200\n\nSince the fix to the recursion detection would allow a single recursion to\nhappen while tracing, this lead to the trace_clock_global() taking a spin\nlock and then trying to take it again:\n\nring_buffer_lock_reserve() {\n  trace_clock_global() {\n    arch_spin_lock() {\n      queued_spin_lock_slowpath() {\n        /* lock taken */\n        (something else gets traced by function graph tracer)\n          ring_buffer_lock_reserve() {\n            trace_clock_global() {\n              arch_spin_lock() {\n                queued_spin_lock_slowpath() {\n                /* DEAD LOCK! */\n\nTracing should *never* block, as it can lead to strange lockups like the\nabove.\n\nRestructure the trace_clock_global() code to instead of simply taking a\nlock to update the recorded \"prev_time\" simply use it, as two events\nhappening on two different CPUs that calls this at the same time, really\ndoesn\u0027t matter which one goes first. Use a trylock to grab the lock for\nupdating the prev_time, and if it fails, simply try again the next time.\nIf it failed to be taken, that means something else is already updating\nit.\n\n\nBugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212761",
  "id": "GHSA-8h6j-vxpr-4ff5",
  "modified": "2024-04-10T21:30:28Z",
  "published": "2024-02-27T21:31:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-46939"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1fca00920327be96f3318224f502e4d5460f9545"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2a1bd74b8186d7938bf004f5603f25b84785f63e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6e2418576228eeb12e7ba82edb8f9500623942ff"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/91ca6f6a91f679c8645d7f3307e03ce86ad518c4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a33614d52e97fc8077eb0b292189ca7d964cc534"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/aafe104aa9096827a429bc1358f8260ee565b7cc"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c64da3294a7d59a4bf6874c664c13be892f15f44"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d43d56dbf452ccecc1ec735cd4b6840118005d7c"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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