CVE-2025-39863 (GCVE-0-2025-39863)

Vulnerability from cvelistv5 – Published: 2025-09-19 15:26 – Updated: 2026-01-14 19:33
VLAI?
Title
wifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoex_info work
Summary
In the Linux kernel, the following vulnerability has been resolved: wifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoex_info work The brcmf_btcoex_detach() only shuts down the btcoex timer, if the flag timer_on is false. However, the brcmf_btcoex_timerfunc(), which runs as timer handler, sets timer_on to false. This creates critical race conditions: 1.If brcmf_btcoex_detach() is called while brcmf_btcoex_timerfunc() is executing, it may observe timer_on as false and skip the call to timer_shutdown_sync(). 2.The brcmf_btcoex_timerfunc() may then reschedule the brcmf_btcoex_info worker after the cancel_work_sync() has been executed, resulting in use-after-free bugs. The use-after-free bugs occur in two distinct scenarios, depending on the timing of when the brcmf_btcoex_info struct is freed relative to the execution of its worker thread. Scenario 1: Freed before the worker is scheduled The brcmf_btcoex_info is deallocated before the worker is scheduled. A race condition can occur when schedule_work(&bt_local->work) is called after the target memory has been freed. The sequence of events is detailed below: CPU0 | CPU1 brcmf_btcoex_detach | brcmf_btcoex_timerfunc | bt_local->timer_on = false; if (cfg->btcoex->timer_on) | ... | cancel_work_sync(); | ... | kfree(cfg->btcoex); // FREE | | schedule_work(&bt_local->work); // USE Scenario 2: Freed after the worker is scheduled The brcmf_btcoex_info is freed after the worker has been scheduled but before or during its execution. In this case, statements within the brcmf_btcoex_handler() — such as the container_of macro and subsequent dereferences of the brcmf_btcoex_info object will cause a use-after-free access. The following timeline illustrates this scenario: CPU0 | CPU1 brcmf_btcoex_detach | brcmf_btcoex_timerfunc | bt_local->timer_on = false; if (cfg->btcoex->timer_on) | ... | cancel_work_sync(); | ... | schedule_work(); // Reschedule | kfree(cfg->btcoex); // FREE | brcmf_btcoex_handler() // Worker /* | btci = container_of(....); // USE The kfree() above could | ... also occur at any point | btci-> // USE during the worker's execution| */ | To resolve the race conditions, drop the conditional check and call timer_shutdown_sync() directly. It can deactivate the timer reliably, regardless of its current state. Once stopped, the timer_on state is then set to false.
Severity ?
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 61730d4dfffc2cc9d3a49fad87633008105c18ba , < f1150153c4e5940fe49ab51136343c5b4fe49d63 (git)
Affected: 61730d4dfffc2cc9d3a49fad87633008105c18ba , < 3e789f8475f6c857c88de5c5bf4b24b11a477dd7 (git)
Affected: 61730d4dfffc2cc9d3a49fad87633008105c18ba , < 2f6fbc8e04ca1d1d5c560be694199f847229c625 (git)
Affected: 61730d4dfffc2cc9d3a49fad87633008105c18ba , < 9cb83d4be0b9b697eae93d321e0da999f9cdfcfc (git)
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    Linux Linux Affected: 3.10
Unaffected: 0 , < 3.10 (semver)
Unaffected: 6.6.105 , ≤ 6.6.* (semver)
Unaffected: 6.12.46 , ≤ 6.12.* (semver)
Unaffected: 6.16.6 , ≤ 6.16.* (semver)
Unaffected: 6.17 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nwifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoex_info work\n\nThe brcmf_btcoex_detach() only shuts down the btcoex timer, if the\nflag timer_on is false. However, the brcmf_btcoex_timerfunc(), which\nruns as timer handler, sets timer_on to false. This creates critical\nrace conditions:\n\n1.If brcmf_btcoex_detach() is called while brcmf_btcoex_timerfunc()\nis executing, it may observe timer_on as false and skip the call to\ntimer_shutdown_sync().\n\n2.The brcmf_btcoex_timerfunc() may then reschedule the brcmf_btcoex_info\nworker after the cancel_work_sync() has been executed, resulting in\nuse-after-free bugs.\n\nThe use-after-free bugs occur in two distinct scenarios, depending on\nthe timing of when the brcmf_btcoex_info struct is freed relative to\nthe execution of its worker thread.\n\nScenario 1: Freed before the worker is scheduled\n\nThe brcmf_btcoex_info is deallocated before the worker is scheduled.\nA race condition can occur when schedule_work(\u0026bt_local-\u003ework) is\ncalled after the target memory has been freed. The sequence of events\nis detailed below:\n\nCPU0                           | CPU1\nbrcmf_btcoex_detach            | brcmf_btcoex_timerfunc\n                               |   bt_local-\u003etimer_on = false;\n  if (cfg-\u003ebtcoex-\u003etimer_on)   |\n    ...                        |\n  cancel_work_sync();          |\n  ...                          |\n  kfree(cfg-\u003ebtcoex); // FREE  |\n                               |   schedule_work(\u0026bt_local-\u003ework); // USE\n\nScenario 2: Freed after the worker is scheduled\n\nThe brcmf_btcoex_info is freed after the worker has been scheduled\nbut before or during its execution. In this case, statements within\nthe brcmf_btcoex_handler() \u2014 such as the container_of macro and\nsubsequent dereferences of the brcmf_btcoex_info object will cause\na use-after-free access. The following timeline illustrates this\nscenario:\n\nCPU0                            | CPU1\nbrcmf_btcoex_detach             | brcmf_btcoex_timerfunc\n                                |   bt_local-\u003etimer_on = false;\n  if (cfg-\u003ebtcoex-\u003etimer_on)    |\n    ...                         |\n  cancel_work_sync();           |\n  ...                           |   schedule_work(); // Reschedule\n                                |\n  kfree(cfg-\u003ebtcoex); // FREE   |   brcmf_btcoex_handler() // Worker\n  /*                            |     btci = container_of(....); // USE\n   The kfree() above could      |     ...\n   also occur at any point      |     btci-\u003e // USE\n   during the worker\u0027s execution|\n   */                           |\n\nTo resolve the race conditions, drop the conditional check and call\ntimer_shutdown_sync() directly. It can deactivate the timer reliably,\nregardless of its current state. Once stopped, the timer_on state is\nthen set to false."
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However, the brcmf_btcoex_timerfunc(), which\\nruns as timer handler, sets timer_on to false. This creates critical\\nrace conditions:\\n\\n1.If brcmf_btcoex_detach() is called while brcmf_btcoex_timerfunc()\\nis executing, it may observe timer_on as false and skip the call to\\ntimer_shutdown_sync().\\n\\n2.The brcmf_btcoex_timerfunc() may then reschedule the brcmf_btcoex_info\\nworker after the cancel_work_sync() has been executed, resulting in\\nuse-after-free bugs.\\n\\nThe use-after-free bugs occur in two distinct scenarios, depending on\\nthe timing of when the brcmf_btcoex_info struct is freed relative to\\nthe execution of its worker thread.\\n\\nScenario 1: Freed before the worker is scheduled\\n\\nThe brcmf_btcoex_info is deallocated before the worker is scheduled.\\nA race condition can occur when schedule_work(\u0026bt_local-\u003ework) is\\ncalled after the target memory has been freed. 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The following timeline illustrates this\\nscenario:\\n\\nCPU0                            | CPU1\\nbrcmf_btcoex_detach             | brcmf_btcoex_timerfunc\\n                                |   bt_local-\u003etimer_on = false;\\n  if (cfg-\u003ebtcoex-\u003etimer_on)    |\\n    ...                         |\\n  cancel_work_sync();           |\\n  ...                           |   schedule_work(); // Reschedule\\n                                |\\n  kfree(cfg-\u003ebtcoex); // FREE   |   brcmf_btcoex_handler() // Worker\\n  /*                            |     btci = container_of(....); // USE\\n   The kfree() above could      |     ...\\n   also occur at any point      |     btci-\u003e // USE\\n   during the worker\u0027s execution|\\n   */                           |\\n\\nTo resolve the race conditions, drop the conditional check and call\\ntimer_shutdown_sync() directly. It can deactivate the timer reliably,\\nregardless of its current state. 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  • 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.
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  • 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.



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