{"api_version":"1","generated_at":"2026-09-11T23:53:30+00:00","cve":"CVE-2026-89460","urls":{"html":"https://cve.report/CVE-2026-89460","api":"https://cve.report/api/cve/CVE-2026-89460.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89460","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89460"},"summary":{"title":"s390/cpum_cf: Handle CPU hotplug via prepare/dead callbacks","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ns390/cpum_cf: Handle CPU hotplug via prepare/dead callbacks\n\nThe command 'perf stat -e cycles -- <command>' crashes the kernel\nwhen CPUs are hotplug added during that run.\n\nRoot cause is the allocation of struct cpu_cf_events at first\nevent initialization. The allocation is dynamic and the first\nevent that has task context creates such a structure for\neach online CPU. This is not sufficient. CPUs may be offline\nduring event creation and can be set online during the\nperf run time. For example commands\n\n # echo 0 > /sys/devices/system/cpu/cpu1/online\n # perf stat -e cycles -i -- stress-ng -t10s --matrix X\n # sleep 1\n # echo 1 > /sys/devices/system/cpu/cpu1/online\n\ncreate an event for CPUs 0,2-X. Since the events are created with\ntask-context, the scheduler will eventually schedule the program\non CPU1. This CPU has not created and initialized any per\nCPU event infrastructure as that CPU was not online at the time\nof the perf invocation. Thus when the scheduler runs stress-ng\non CPU1, the function cpumf_pmu_add() refers to a NULL pointer:\n\n struct cpu_cf_events *cpuhw = this_cpu_cfhw();\n\nThis function call is invoked after the task stress-ng has been\nmade runnable on CPU1. And this_cpu_cfhw() returns NULL.\n\nThe result is a panic:\nUnable to handle kernel pointer dereference in virtual kernel address space\nFailing address: 0000000000000000 TEID: 0000000000000483\n....\nKrnl PSW : 0404d00180000000 000003ef8291fd0c (cpumf_pmu_add+0x3c/0x80)\n....\nCall Trace:\n [<000003ef8291fd0c>] cpumf_pmu_add+0x3c/0x80\n [<000003ef82bb5e3e>] event_sched_in+0xae/0x190\n [<000003ef82bb60d6>] merge_sched_in+0x1b6/0x390\n [<000003ef82bb65b8>] visit_groups_merge.constprop.0.isra.0+0x308/0x5b0\n [<000003ef82bb689a>] pmu_groups_sched_in+0x3a/0x50\n [<000003ef82bb6a30>] ctx_sched_in+0x180/0x260\n [<000003ef82bb780c>] perf_event_context_sched_in+0x11c/0x2d0\n [<000003ef82bb79ee>] __perf_event_task_sched_in+0x2e/0xc0\n [<000003ef82994834>] finish_task_switch.isra.0+0x1a4/0x250\n....\nLast Breaking-Event-Address:\n [<000003ef8291f1d8>] this_cpu_cfhw+0x38/0x40\n\nThe issue arises only in per-task context when the CPUMF facility is\nused and the scheduler picks a random CPU for such a process to run on.\nThe scheduler enables the CPUMF infrastructure via PMU callback\nfunctions pmu::add() and pmu::del().\n\nIntroduce a CPU hotplug prepare/dead callback pair which creates and\nremoves the per CPU counter data while the CPU is offline. Count the\nusers which track every CPU (cpu == -1), that is perf_event_open()\nevents with task context and /dev/hwctr device sessions, in the new\ncounter cpu_cf_root::tskcnt, protected by pmc_reserve_mutex.\nThis ensures the infrastructure is available when\nnew CPU is selected to run the per-task context process.\n\nIn cpum_cf_free_root() and cpum_cf_free_cpu() ensure the reference\npointer to data structures is set to NULL before the data is freed\nto prevent interrupt handlers to access stale data.\n\n[gor@linux.ibm.com: change commit message]","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:26","updated_at":"2026-09-11 20:19:26"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/337bd95507a16063687cfc286ea90de5cca48c37","name":"https://git.kernel.org/stable/c/337bd95507a16063687cfc286ea90de5cca48c37","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/777d040c2f91d8d929b4a32333dfe4102b27caea","name":"https://git.kernel.org/stable/c/777d040c2f91d8d929b4a32333dfe4102b27caea","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/71d46de9153e067c63a15f3b00e6364e1c0230f8","name":"https://git.kernel.org/stable/c/71d46de9153e067c63a15f3b00e6364e1c0230f8","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/dcce7a06ea690d5cf46a705a9b74cf0398ac091f","name":"https://git.kernel.org/stable/c/dcce7a06ea690d5cf46a705a9b74cf0398ac091f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89460","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89460","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9b9cf3c77e7e090b30657b3d2c288deb58dfb4f2 777d040c2f91d8d929b4a32333dfe4102b27caea git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9b9cf3c77e7e090b30657b3d2c288deb58dfb4f2 dcce7a06ea690d5cf46a705a9b74cf0398ac091f git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9b9cf3c77e7e090b30657b3d2c288deb58dfb4f2 71d46de9153e067c63a15f3b00e6364e1c0230f8 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9b9cf3c77e7e090b30657b3d2c288deb58dfb4f2 337bd95507a16063687cfc286ea90de5cca48c37 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.5","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.5 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.109 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.50 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.4 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["arch/s390/kernel/perf_cpum_cf.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"777d040c2f91d8d929b4a32333dfe4102b27caea","status":"affected","version":"9b9cf3c77e7e090b30657b3d2c288deb58dfb4f2","versionType":"git"},{"lessThan":"dcce7a06ea690d5cf46a705a9b74cf0398ac091f","status":"affected","version":"9b9cf3c77e7e090b30657b3d2c288deb58dfb4f2","versionType":"git"},{"lessThan":"71d46de9153e067c63a15f3b00e6364e1c0230f8","status":"affected","version":"9b9cf3c77e7e090b30657b3d2c288deb58dfb4f2","versionType":"git"},{"lessThan":"337bd95507a16063687cfc286ea90de5cca48c37","status":"affected","version":"9b9cf3c77e7e090b30657b3d2c288deb58dfb4f2","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["arch/s390/kernel/perf_cpum_cf.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.5"},{"lessThan":"6.5","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.109","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.50","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.4","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.109","versionStartIncluding":"6.5","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.50","versionStartIncluding":"6.5","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"6.5","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"6.5","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ns390/cpum_cf: Handle CPU hotplug via prepare/dead callbacks\n\nThe command 'perf stat -e cycles -- <command>' crashes the kernel\nwhen CPUs are hotplug added during that run.\n\nRoot cause is the allocation of struct cpu_cf_events at first\nevent initialization. The allocation is dynamic and the first\nevent that has task context creates such a structure for\neach online CPU. This is not sufficient. CPUs may be offline\nduring event creation and can be set online during the\nperf run time. For example commands\n\n # echo 0 > /sys/devices/system/cpu/cpu1/online\n # perf stat -e cycles -i -- stress-ng -t10s --matrix X\n # sleep 1\n # echo 1 > /sys/devices/system/cpu/cpu1/online\n\ncreate an event for CPUs 0,2-X. Since the events are created with\ntask-context, the scheduler will eventually schedule the program\non CPU1. This CPU has not created and initialized any per\nCPU event infrastructure as that CPU was not online at the time\nof the perf invocation. Thus when the scheduler runs stress-ng\non CPU1, the function cpumf_pmu_add() refers to a NULL pointer:\n\n struct cpu_cf_events *cpuhw = this_cpu_cfhw();\n\nThis function call is invoked after the task stress-ng has been\nmade runnable on CPU1. And this_cpu_cfhw() returns NULL.\n\nThe result is a panic:\nUnable to handle kernel pointer dereference in virtual kernel address space\nFailing address: 0000000000000000 TEID: 0000000000000483\n....\nKrnl PSW : 0404d00180000000 000003ef8291fd0c (cpumf_pmu_add+0x3c/0x80)\n....\nCall Trace:\n [<000003ef8291fd0c>] cpumf_pmu_add+0x3c/0x80\n [<000003ef82bb5e3e>] event_sched_in+0xae/0x190\n [<000003ef82bb60d6>] merge_sched_in+0x1b6/0x390\n [<000003ef82bb65b8>] visit_groups_merge.constprop.0.isra.0+0x308/0x5b0\n [<000003ef82bb689a>] pmu_groups_sched_in+0x3a/0x50\n [<000003ef82bb6a30>] ctx_sched_in+0x180/0x260\n [<000003ef82bb780c>] perf_event_context_sched_in+0x11c/0x2d0\n [<000003ef82bb79ee>] __perf_event_task_sched_in+0x2e/0xc0\n [<000003ef82994834>] finish_task_switch.isra.0+0x1a4/0x250\n....\nLast Breaking-Event-Address:\n [<000003ef8291f1d8>] this_cpu_cfhw+0x38/0x40\n\nThe issue arises only in per-task context when the CPUMF facility is\nused and the scheduler picks a random CPU for such a process to run on.\nThe scheduler enables the CPUMF infrastructure via PMU callback\nfunctions pmu::add() and pmu::del().\n\nIntroduce a CPU hotplug prepare/dead callback pair which creates and\nremoves the per CPU counter data while the CPU is offline. Count the\nusers which track every CPU (cpu == -1), that is perf_event_open()\nevents with task context and /dev/hwctr device sessions, in the new\ncounter cpu_cf_root::tskcnt, protected by pmc_reserve_mutex.\nThis ensures the infrastructure is available when\nnew CPU is selected to run the per-task context process.\n\nIn cpum_cf_free_root() and cpum_cf_free_cpu() ensure the reference\npointer to data structures is set to NULL before the data is freed\nto prevent interrupt handlers to access stale data.\n\n[gor@linux.ibm.com: change commit message]"}],"providerMetadata":{"dateUpdated":"2026-09-11T19:43:22.664Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/777d040c2f91d8d929b4a32333dfe4102b27caea"},{"url":"https://git.kernel.org/stable/c/dcce7a06ea690d5cf46a705a9b74cf0398ac091f"},{"url":"https://git.kernel.org/stable/c/71d46de9153e067c63a15f3b00e6364e1c0230f8"},{"url":"https://git.kernel.org/stable/c/337bd95507a16063687cfc286ea90de5cca48c37"}],"title":"s390/cpum_cf: Handle CPU hotplug via prepare/dead callbacks","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89460","datePublished":"2026-09-11T19:43:22.664Z","dateReserved":"2026-09-11T19:38:34.708Z","dateUpdated":"2026-09-11T19:43:22.664Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:26","lastModifiedDate":"2026-09-11 20:19:26","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89460","Ordinal":"1","Title":"s390/cpum_cf: Handle CPU hotplug via prepare/dead callbacks","CVE":"CVE-2026-89460","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89460","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\ns390/cpum_cf: Handle CPU hotplug via prepare/dead callbacks\n\nThe command 'perf stat -e cycles -- <command>' crashes the kernel\nwhen CPUs are hotplug added during that run.\n\nRoot cause is the allocation of struct cpu_cf_events at first\nevent initialization. The allocation is dynamic and the first\nevent that has task context creates such a structure for\neach online CPU. This is not sufficient. CPUs may be offline\nduring event creation and can be set online during the\nperf run time. For example commands\n\n # echo 0 > /sys/devices/system/cpu/cpu1/online\n # perf stat -e cycles -i -- stress-ng -t10s --matrix X\n # sleep 1\n # echo 1 > /sys/devices/system/cpu/cpu1/online\n\ncreate an event for CPUs 0,2-X. Since the events are created with\ntask-context, the scheduler will eventually schedule the program\non CPU1. This CPU has not created and initialized any per\nCPU event infrastructure as that CPU was not online at the time\nof the perf invocation. Thus when the scheduler runs stress-ng\non CPU1, the function cpumf_pmu_add() refers to a NULL pointer:\n\n struct cpu_cf_events *cpuhw = this_cpu_cfhw();\n\nThis function call is invoked after the task stress-ng has been\nmade runnable on CPU1. And this_cpu_cfhw() returns NULL.\n\nThe result is a panic:\nUnable to handle kernel pointer dereference in virtual kernel address space\nFailing address: 0000000000000000 TEID: 0000000000000483\n....\nKrnl PSW : 0404d00180000000 000003ef8291fd0c (cpumf_pmu_add+0x3c/0x80)\n....\nCall Trace:\n [<000003ef8291fd0c>] cpumf_pmu_add+0x3c/0x80\n [<000003ef82bb5e3e>] event_sched_in+0xae/0x190\n [<000003ef82bb60d6>] merge_sched_in+0x1b6/0x390\n [<000003ef82bb65b8>] visit_groups_merge.constprop.0.isra.0+0x308/0x5b0\n [<000003ef82bb689a>] pmu_groups_sched_in+0x3a/0x50\n [<000003ef82bb6a30>] ctx_sched_in+0x180/0x260\n [<000003ef82bb780c>] perf_event_context_sched_in+0x11c/0x2d0\n [<000003ef82bb79ee>] __perf_event_task_sched_in+0x2e/0xc0\n [<000003ef82994834>] finish_task_switch.isra.0+0x1a4/0x250\n....\nLast Breaking-Event-Address:\n [<000003ef8291f1d8>] this_cpu_cfhw+0x38/0x40\n\nThe issue arises only in per-task context when the CPUMF facility is\nused and the scheduler picks a random CPU for such a process to run on.\nThe scheduler enables the CPUMF infrastructure via PMU callback\nfunctions pmu::add() and pmu::del().\n\nIntroduce a CPU hotplug prepare/dead callback pair which creates and\nremoves the per CPU counter data while the CPU is offline. Count the\nusers which track every CPU (cpu == -1), that is perf_event_open()\nevents with task context and /dev/hwctr device sessions, in the new\ncounter cpu_cf_root::tskcnt, protected by pmc_reserve_mutex.\nThis ensures the infrastructure is available when\nnew CPU is selected to run the per-task context process.\n\nIn cpum_cf_free_root() and cpum_cf_free_cpu() ensure the reference\npointer to data structures is set to NULL before the data is freed\nto prevent interrupt handlers to access stale data.\n\n[gor@linux.ibm.com: change commit message]","Type":"Description","Title":"s390/cpum_cf: Handle CPU hotplug via prepare/dead callbacks"}]}}}