{"id":"CVE-2025-37878","title":"perf/core: Fix WARN_ON(!ctx) in __free_event() for partial init","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Fix WARN_ON(!ctx) in __free_event() for partial init\n\nMove the get_ctx(child_ctx) call and the child_event->ctx assignment to\noccur immediately after the chi…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 7ef5aa081f989ecfecc1df02068a80aebbd3ec31 < 90dc6c1e3b200812da8d0aa030e1b7fda8226d0e","Linux >= 1209b0b29fd472e7dbd2b06544b019dd9f9b7e51 < cb56cd11feabf99e08bc18960700a53322ffcea7","Linux >= c70ca298036c58a88686ff388d3d367e9d21acf0 < 0ba3a4ab76fd3367b9cb680cad70182c896c795c","Linux 315a50c6b1c6ce191f19f3372935d8e2ed9b53a6","Linux >= 6.13.12 < 6.14","Linux >= 6.12.24 < 6.12.26","Linux >= 6.14.3 < 6.14.5"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-05T20:44:23.606659Z"},"published":"2025-05-09","updated":"2026-11-05","sourceUpdated":"2026-11-05T20:52:06.591Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-37878","references":[{"url":"https://git.kernel.org/stable/c/90dc6c1e3b200812da8d0aa030e1b7fda8226d0e"},{"url":"https://git.kernel.org/stable/c/cb56cd11feabf99e08bc18960700a53322ffcea7"},{"url":"https://git.kernel.org/stable/c/0ba3a4ab76fd3367b9cb680cad70182c896c795c"}],"tags":["cve.org"],"epss":0.00276,"epssPercentile":0.20112,"ingestedAt":"2026-11-05T22:38:31.888Z","slug":"CVE-2025-37878","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Fix WARN_ON(!ctx) in __free_event() for partial init\n\nMove the get_ctx(child_ctx) call and the child_event->ctx assignment to\noccur immediately after the child event is allocated. Ensure that\nchild_event->ctx is non-NULL before any subsequent error path within\ninherit_event calls free_event(), satisfying the assumptions of the\ncleanup code.\n\nDetails:\n\nThere's no clear Fixes tag, because this bug is a side-effect of\nmultiple interacting commits over time (up to 15 years old), not\na single regression.\n\nThe code initially incremented refcount then assigned context\nimmediately after the child_event was created. Later, an early\nvalidity check for child_event was added before the\nrefcount/assignment. Even later, a WARN_ON_ONCE() cleanup check was\nadded, assuming event->ctx is valid if the pmu_ctx is valid.\nThe problem is that the WARN_ON_ONCE() could trigger after the initial\ncheck passed but before child_event->ctx was assigned, violating its\nprecondition. The solution is to assign child_event->ctx right after\nits initial validation. This ensures the context exists for any\nsubsequent checks or cleanup routines, resolving the WARN_ON_ONCE().\n\nTo resolve it, defer the refcount update and child_event->ctx assignment\ndirectly after child_event->pmu_ctx is set but before checking if the\nparent event is orphaned. The cleanup routine depends on\nevent->pmu_ctx being non-NULL before it verifies event->ctx is\nnon-NULL. This also maintains the author's original intent of passing\nin child_ctx to find_get_pmu_context before its refcount/assignment.\n\n[ mingo: Expanded the changelog from another email by Gabriel Shahrouzi. ]\n\n## Affected\n\n- `Linux >= 7ef5aa081f989ecfecc1df02068a80aebbd3ec31 < 90dc6c1e3b200812da8d0aa030e1b7fda8226d0e`\n- `Linux >= 1209b0b29fd472e7dbd2b06544b019dd9f9b7e51 < cb56cd11feabf99e08bc18960700a53322ffcea7`\n- `Linux >= c70ca298036c58a88686ff388d3d367e9d21acf0 < 0ba3a4ab76fd3367b9cb680cad70182c896c795c`\n- `Linux 315a50c6b1c6ce191f19f3372935d8e2ed9b53a6`\n- `Linux >= 6.13.12 < 6.14`\n- `Linux >= 6.12.24 < 6.12.26`\n- `Linux >= 6.14.3 < 6.14.5`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}