{"id":"DEBIAN-CVE-2025-37878","details":"In the Linux kernel, the following vulnerability has been resolved:  perf/core: Fix WARN_ON(!ctx) in __free_event() for partial init  Move the get_ctx(child_ctx) call and the child_event-\u003ectx assignment to occur immediately after the child event is allocated. Ensure that child_event-\u003ectx is non-NULL before any subsequent error path within inherit_event calls free_event(), satisfying the assumptions of the cleanup code.  Details:  There's no clear Fixes tag, because this bug is a side-effect of multiple interacting commits over time (up to 15 years old), not a single regression.  The code initially incremented refcount then assigned context immediately after the child_event was created. Later, an early validity check for child_event was added before the refcount/assignment. Even later, a WARN_ON_ONCE() cleanup check was added, assuming event-\u003ectx is valid if the pmu_ctx is valid. The problem is that the WARN_ON_ONCE() could trigger after the initial check passed but before child_event-\u003ectx was assigned, violating its precondition. The solution is to assign child_event-\u003ectx right after its initial validation. This ensures the context exists for any subsequent checks or cleanup routines, resolving the WARN_ON_ONCE().  To resolve it, defer the refcount update and child_event-\u003ectx assignment directly after child_event-\u003epmu_ctx is set but before checking if the parent event is orphaned. The cleanup routine depends on event-\u003epmu_ctx being non-NULL before it verifies event-\u003ectx is non-NULL. This also maintains the author's original intent of passing in child_ctx to find_get_pmu_context before its refcount/assignment.  [ mingo: Expanded the changelog from another email by Gabriel Shahrouzi. ]","modified":"2026-08-27T23:05:28.702333838Z","published":"2025-05-09T07:16:09.020Z","upstream":["CVE-2025-37878"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2025-37878"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.27-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-37878.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.27-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-37878.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}