[SRU][N][PATCH 0/1] CVE-2025-38565

[Cengiz Can]

https://ubuntu.com/security/CVE-2025-38565

[ Impact ]

In the Linux kernel, the following vulnerability has been resolved:

perf/core: Exit early on perf_mmap() fail

When perf_mmap() fails to allocate a buffer, it still invokes the
event_mapped() callback of the related event. On X86 this might increase the
perf_rdpmc_allowed reference counter. But nothing undoes this as
perf_mmap_close() is never called in this case, which causes another reference
count leak.

Return early on failure to prevent that.

[ Fix ]

noble/linux: backported from 07091aade394

The upstream change was reworked around a map_range/get_mapped refactor that
is not present in this tree. The backport keeps the essential early exit that
returns before the event_mapped() callback runs, and continues to use the
older event->pmu->event_mapped() callback directly.

[ Test Plan ]

Build and boot tested.

[ Where Problems Could Occur ]

The change touches the perf_mmap() path in the core perf subsystem, so a bad
fix could affect X86 systems running profiling or performance-monitoring
tools that map perf ring buffers, particularly workloads that rely on
userspace rdpmc access. Users who do not use perf event mmap or rdpmc, and
non-X86 architectures where perf_rdpmc_allowed is not maintained, are not
affected by this code.

[ Other Info ]

Kybele flow-v11-25-ga27c0fa6. Reference: d74fd480/v1