165 lines
10 KiB
JSON
165 lines
10 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-23435",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-01-13T15:37:46.017Z",
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"datePublished": "2026-04-03T15:15:20.465Z",
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"dateUpdated": "2026-05-23T16:04:50.015Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-05-23T16:04:50.015Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/x86: Move event pointer setup earlier in x86_pmu_enable()\n\nA production AMD EPYC system crashed with a NULL pointer dereference\nin the PMU NMI handler:\n\n BUG: kernel NULL pointer dereference, address: 0000000000000198\n RIP: x86_perf_event_update+0xc/0xa0\n Call Trace:\n <NMI>\n amd_pmu_v2_handle_irq+0x1a6/0x390\n perf_event_nmi_handler+0x24/0x40\n\nThe faulting instruction is `cmpq $0x0, 0x198(%rdi)` with RDI=0,\ncorresponding to the `if (unlikely(!hwc->event_base))` check in\nx86_perf_event_update() where hwc = &event->hw and event is NULL.\n\ndrgn inspection of the vmcore on CPU 106 showed a mismatch between\ncpuc->active_mask and cpuc->events[]:\n\n active_mask: 0x1e (bits 1, 2, 3, 4)\n events[1]: 0xff1100136cbd4f38 (valid)\n events[2]: 0x0 (NULL, but active_mask bit 2 set)\n events[3]: 0xff1100076fd2cf38 (valid)\n events[4]: 0xff1100079e990a90 (valid)\n\nThe event that should occupy events[2] was found in event_list[2]\nwith hw.idx=2 and hw.state=0x0, confirming x86_pmu_start() had run\n(which clears hw.state and sets active_mask) but events[2] was\nnever populated.\n\nAnother event (event_list[0]) had hw.state=0x7 (STOPPED|UPTODATE|ARCH),\nshowing it was stopped when the PMU rescheduled events, confirming the\nthrottle-then-reschedule sequence occurred.\n\nThe root cause is commit 7e772a93eb61 (\"perf/x86: Fix NULL event access\nand potential PEBS record loss\") which moved the cpuc->events[idx]\nassignment out of x86_pmu_start() and into step 2 of x86_pmu_enable(),\nafter the PERF_HES_ARCH check. This broke any path that calls\npmu->start() without going through x86_pmu_enable() -- specifically\nthe unthrottle path:\n\n perf_adjust_freq_unthr_events()\n -> perf_event_unthrottle_group()\n -> perf_event_unthrottle()\n -> event->pmu->start(event, 0)\n -> x86_pmu_start() // sets active_mask but not events[]\n\nThe race sequence is:\n\n 1. A group of perf events overflows, triggering group throttle via\n perf_event_throttle_group(). All events are stopped: active_mask\n bits cleared, events[] preserved (x86_pmu_stop no longer clears\n events[] after commit 7e772a93eb61).\n\n 2. While still throttled (PERF_HES_STOPPED), x86_pmu_enable() runs\n due to other scheduling activity. Stopped events that need to\n move counters get PERF_HES_ARCH set and events[old_idx] cleared.\n In step 2 of x86_pmu_enable(), PERF_HES_ARCH causes these events\n to be skipped -- events[new_idx] is never set.\n\n 3. The timer tick unthrottles the group via pmu->start(). Since\n commit 7e772a93eb61 removed the events[] assignment from\n x86_pmu_start(), active_mask[new_idx] is set but events[new_idx]\n remains NULL.\n\n 4. A PMC overflow NMI fires. The handler iterates active counters,\n finds active_mask[2] set, reads events[2] which is NULL, and\n crashes dereferencing it.\n\nMove the cpuc->events[hwc->idx] assignment in x86_pmu_enable() to\nbefore the PERF_HES_ARCH check, so that events[] is populated even\nfor events that are not immediately started. This ensures the\nunthrottle path via pmu->start() always finds a valid event pointer."
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"arch/x86/events/core.c"
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],
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"versions": [
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{
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"version": "6b089028bff1f2ff9e0c62b8f1faca1a620e5d6e",
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"lessThan": "886fa869153917d902784098922defa20c3a2fe5",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "7e772a93eb61cb6265bdd1c5bde17d0f2718b452",
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"lessThan": "c1dd1e2b722d3f1f2e4977dad8d1be78fdfb30cb",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "7e772a93eb61cb6265bdd1c5bde17d0f2718b452",
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"lessThan": "8d5fae6011260de209aaf231120e8146b14bc8e0",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "cf69b99805c263117305ac6dffbc85aaf9259d32",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "6.18.2",
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"lessThan": "6.18.20",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "6.17.13",
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"lessThan": "6.18",
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"status": "affected",
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"versionType": "semver"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"arch/x86/events/core.c"
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],
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"versions": [
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{
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"version": "6.19",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "6.19",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.18.20",
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"lessThanOrEqual": "6.18.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.19.10",
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"lessThanOrEqual": "6.19.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.0",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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],
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"cpeApplicability": [
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{
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"nodes": [
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{
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"operator": "OR",
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"negate": false,
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"cpeMatch": [
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.18.2",
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"versionEndExcluding": "6.18.20"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.19",
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"versionEndExcluding": "6.19.10"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.19",
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"versionEndExcluding": "7.0"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.17.13"
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}
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]
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}
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]
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}
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],
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/886fa869153917d902784098922defa20c3a2fe5"
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},
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{
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"url": "https://git.kernel.org/stable/c/c1dd1e2b722d3f1f2e4977dad8d1be78fdfb30cb"
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},
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{
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"url": "https://git.kernel.org/stable/c/8d5fae6011260de209aaf231120e8146b14bc8e0"
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}
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],
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"title": "perf/x86: Move event pointer setup earlier in x86_pmu_enable()",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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}
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}
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} |