{"id":"AZL-70150","summary":"CVE-2025-37878 affecting package kernel 5.15.200.1-1","details":"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-\u003ectx assignment to\noccur immediately after the child event is allocated. Ensure that\nchild_event-\u003ectx 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-\u003ectx 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-\u003ectx was assigned, violating its\nprecondition. The solution is to assign child_event-\u003ectx 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-\u003ectx assignment\ndirectly after child_event-\u003epmu_ctx is set but before checking if the\nparent event is orphaned. The cleanup routine depends on\nevent-\u003epmu_ctx being non-NULL before it verifies event-\u003ectx 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. ]","modified":"2026-04-01T05:21:42.078680Z","published":"2025-05-09T07:16:09Z","upstream":["CVE-2025-37878"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-37878"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:2","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"5.15.200.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-70150.json"}}],"schema_version":"1.7.5"}