{"api_version":"1","generated_at":"2026-07-23T14:15:21+00:00","cve":"CVE-2025-39863","urls":{"html":"https://cve.report/CVE-2025-39863","api":"https://cve.report/api/cve/CVE-2025-39863.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2025-39863","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2025-39863"},"summary":{"title":"wifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoex_info work","description":"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(&bt_local->work) 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->timer_on = false;\n  if (cfg->btcoex->timer_on)   |\n    ...                        |\n  cancel_work_sync();          |\n  ...                          |\n  kfree(cfg->btcoex); // FREE  |\n                               |   schedule_work(&bt_local->work); // 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() — 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->timer_on = false;\n  if (cfg->btcoex->timer_on)    |\n    ...                         |\n  cancel_work_sync();           |\n  ...                           |   schedule_work(); // Reschedule\n                                |\n  kfree(cfg->btcoex); // FREE   |   brcmf_btcoex_handler() // Worker\n  /*                            |     btci = container_of(....); // USE\n   The kfree() above could      |     ...\n   also occur at any point      |     btci-> // USE\n   during the worker's 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.","state":"PUBLISHED","assigner":"Linux","published_at":"2025-09-19 16:15:45","updated_at":"2026-06-19 13:16:22"},"problem_types":["CWE-416","CWE-416 CWE-416 Use After Free"],"metrics":[{"version":"3.1","source":"nvd@nist.gov","type":"Primary","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"ADP","type":"DECLARED","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":7.8,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}},{"version":"3.1","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}}],"references":[{"url":"https://git.kernel.org/stable/c/2f6fbc8e04ca1d1d5c560be694199f847229c625","name":"https://git.kernel.org/stable/c/2f6fbc8e04ca1d1d5c560be694199f847229c625","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ae58f70bde0433f27ef4b388ab50634736607bf6","name":"https://git.kernel.org/stable/c/ae58f70bde0433f27ef4b388ab50634736607bf6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/9cb83d4be0b9b697eae93d321e0da999f9cdfcfc","name":"https://git.kernel.org/stable/c/9cb83d4be0b9b697eae93d321e0da999f9cdfcfc","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/3e789f8475f6c857c88de5c5bf4b24b11a477dd7","name":"https://git.kernel.org/stable/c/3e789f8475f6c857c88de5c5bf4b24b11a477dd7","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/c75600e69e66a751cc046cd9c407b942f298d852","name":"https://git.kernel.org/stable/c/c75600e69e66a751cc046cd9c407b942f298d852","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f1150153c4e5940fe49ab51136343c5b4fe49d63","name":"https://git.kernel.org/stable/c/f1150153c4e5940fe49ab51136343c5b4fe49d63","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2025-39863","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39863","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61730d4dfffc2cc9d3a49fad87633008105c18ba c75600e69e66a751cc046cd9c407b942f298d852 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61730d4dfffc2cc9d3a49fad87633008105c18ba ae58f70bde0433f27ef4b388ab50634736607bf6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61730d4dfffc2cc9d3a49fad87633008105c18ba f1150153c4e5940fe49ab51136343c5b4fe49d63 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61730d4dfffc2cc9d3a49fad87633008105c18ba 3e789f8475f6c857c88de5c5bf4b24b11a477dd7 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61730d4dfffc2cc9d3a49fad87633008105c18ba 2f6fbc8e04ca1d1d5c560be694199f847229c625 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61730d4dfffc2cc9d3a49fad87633008105c18ba 9cb83d4be0b9b697eae93d321e0da999f9cdfcfc git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3.10","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 3.10 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.210 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.167 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.105 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.46 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.16.6 6.16.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.17 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[{"cve_year":"2025","cve_id":"39863","vulnerable":"1","versionEndIncluding":"","cpe1":"cpe","cpe2":"2.3","cpe3":"o","cpe4":"linux","cpe5":"linux_kernel","cpe6":"*","cpe7":"*","cpe8":"*","cpe9":"*","cpe10":"*","cpe11":"*","cpe12":"*","cpe13":"*"}],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":7.8,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}},{"other":{"content":{"id":"CVE-2025-39863","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","timestamp":"2026-01-14T19:23:53.735650Z","version":"2.0.3"},"type":"ssvc"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","description":"CWE-416 Use After Free","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-01-14T19:33:11.612Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["drivers/net/wireless/broadcom/brcm80211/brcmfmac/btcoex.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"c75600e69e66a751cc046cd9c407b942f298d852","status":"affected","version":"61730d4dfffc2cc9d3a49fad87633008105c18ba","versionType":"git"},{"lessThan":"ae58f70bde0433f27ef4b388ab50634736607bf6","status":"affected","version":"61730d4dfffc2cc9d3a49fad87633008105c18ba","versionType":"git"},{"lessThan":"f1150153c4e5940fe49ab51136343c5b4fe49d63","status":"affected","version":"61730d4dfffc2cc9d3a49fad87633008105c18ba","versionType":"git"},{"lessThan":"3e789f8475f6c857c88de5c5bf4b24b11a477dd7","status":"affected","version":"61730d4dfffc2cc9d3a49fad87633008105c18ba","versionType":"git"},{"lessThan":"2f6fbc8e04ca1d1d5c560be694199f847229c625","status":"affected","version":"61730d4dfffc2cc9d3a49fad87633008105c18ba","versionType":"git"},{"lessThan":"9cb83d4be0b9b697eae93d321e0da999f9cdfcfc","status":"affected","version":"61730d4dfffc2cc9d3a49fad87633008105c18ba","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["drivers/net/wireless/broadcom/brcm80211/brcmfmac/btcoex.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"3.10"},{"lessThan":"3.10","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.210","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.167","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.105","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.46","versionType":"semver"},{"lessThanOrEqual":"6.16.*","status":"unaffected","version":"6.16.6","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"6.17","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.210","versionStartIncluding":"3.10","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.167","versionStartIncluding":"3.10","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.105","versionStartIncluding":"3.10","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.46","versionStartIncluding":"3.10","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.16.6","versionStartIncluding":"3.10","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.17","versionStartIncluding":"3.10","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","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(&bt_local->work) 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->timer_on = false;\n  if (cfg->btcoex->timer_on)   |\n    ...                        |\n  cancel_work_sync();          |\n  ...                          |\n  kfree(cfg->btcoex); // FREE  |\n                               |   schedule_work(&bt_local->work); // 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() — 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->timer_on = false;\n  if (cfg->btcoex->timer_on)    |\n    ...                         |\n  cancel_work_sync();           |\n  ...                           |   schedule_work(); // Reschedule\n                                |\n  kfree(cfg->btcoex); // FREE   |   brcmf_btcoex_handler() // Worker\n  /*                            |     btci = container_of(....); // USE\n   The kfree() above could      |     ...\n   also occur at any point      |     btci-> // USE\n   during the worker's 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."}],"providerMetadata":{"dateUpdated":"2026-06-19T11:57:19.623Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/c75600e69e66a751cc046cd9c407b942f298d852"},{"url":"https://git.kernel.org/stable/c/ae58f70bde0433f27ef4b388ab50634736607bf6"},{"url":"https://git.kernel.org/stable/c/f1150153c4e5940fe49ab51136343c5b4fe49d63"},{"url":"https://git.kernel.org/stable/c/3e789f8475f6c857c88de5c5bf4b24b11a477dd7"},{"url":"https://git.kernel.org/stable/c/2f6fbc8e04ca1d1d5c560be694199f847229c625"},{"url":"https://git.kernel.org/stable/c/9cb83d4be0b9b697eae93d321e0da999f9cdfcfc"}],"title":"wifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoex_info work","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2025-39863","datePublished":"2025-09-19T15:26:33.069Z","dateReserved":"2025-04-16T07:20:57.143Z","dateUpdated":"2026-06-19T11:57:19.623Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2025-09-19 16:15:45","lastModifiedDate":"2026-06-19 13:16:22","problem_types":["CWE-416","CWE-416 CWE-416 Use After Free"],"metrics":{"cvssMetricV31":[{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":5.9},{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":5.9}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-01-14T19:23:53.735650Z","id":"CVE-2025-39863","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.10","versionEndExcluding":"6.6.105","matchCriteriaId":"D5818F4E-9CA3-4FE9-8A75-A6ACE2B108FC"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.12.46","matchCriteriaId":"F7E2B332-E920-4CAC-B400-288602DB6F16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"6.16.6","matchCriteriaId":"548F104C-0F08-438B-9C97-64C903F0C678"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*","matchCriteriaId":"327D22EF-390B-454C-BD31-2ED23C998A1C"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*","matchCriteriaId":"C730CD9A-D969-4A8E-9522-162AAF7C0EE9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*","matchCriteriaId":"39982C4B-716E-4B2F-8196-FA301F47807D"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:*","matchCriteriaId":"340BEEA9-D70D-4290-B502-FBB1032353B1"}]}]}]},"legacy_mitre":{"record":{"CveYear":"2025","CveId":"39863","Ordinal":"1","Title":"wifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoe","CVE":"CVE-2025-39863","Year":"2025"},"notes":[{"CveYear":"2025","CveId":"39863","Ordinal":"1","NoteData":"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(&bt_local->work) 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->timer_on = false;\n  if (cfg->btcoex->timer_on)   |\n    ...                        |\n  cancel_work_sync();          |\n  ...                          |\n  kfree(cfg->btcoex); // FREE  |\n                               |   schedule_work(&bt_local->work); // 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() — 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->timer_on = false;\n  if (cfg->btcoex->timer_on)    |\n    ...                         |\n  cancel_work_sync();           |\n  ...                           |   schedule_work(); // Reschedule\n                                |\n  kfree(cfg->btcoex); // FREE   |   brcmf_btcoex_handler() // Worker\n  /*                            |     btci = container_of(....); // USE\n   The kfree() above could      |     ...\n   also occur at any point      |     btci-> // USE\n   during the worker's 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.","Type":"Description","Title":"wifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoe"}]}}}