CVE-2026-52973

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

futex: Drop CLONE_THREAD requirement for private default hash alloc

Currently need_futex_hash_allocate_default() depends on strict pthread

semantics, abusing CLONE_THREAD. This breaks the non-concurrency

assumptions when doing the mm->futex_ref pcpu allocations, leading to

bugs[0] when sharing the mm in other ways; ie:

BUG: KASAN: slab-use-after-free in futex_hash_put

... where the +1 bias can end up on a percpu counter that mm->futex_ref

no longer points at.

Loosen the check to cover any CLONE_VM clone, except vfork(). Excluding

vfork keeps the existing paths untouched (no overhead), and we can't

race in the first place: either the parent is suspended and the child

runs alone, or mm->futex_ref is already allocated from an earlier

CLONE_VM.