CVE-2026-23127 perf: Fix refcount warning on event->mmap_count increment

In the Linux kernel, the following vulnerability has been resolved: perf: Fix refcount warning on event-mmapcount increment When calling refcountinc&event-mmapcount inside perfmmaprb, the following warning is triggered: refcountt: addition on 0; use-after-free. WARNING: lib/refcount.c:25 PoC:...

CVE-2026-23127

CVE-2026-23127 affects the Linux kernel perf subsystem. The issue is caused by a refcount warning in perf_mmap_rb() when updating event->mmap_count during group-member mmap creation with PERF_FLAG_FD_OUTPUT. Specifically, refcount_inc(&event->mmap_count) can run when mmap_count is 0, trigge...