futex: Also allocate private hash on vfork()

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As Jann demonstrated, it is entirely feasible to access the mm through vfork().
Therefore we need to allocate a private hash on vfork() as well as any other
CLONE_VM user.

Specifically, it must be avoided to have (private) futex waiters before
allocating the private hash.

Fixes: ee9dce4436 ("futex: Drop CLONE_THREAD requirement for private default hash alloc")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260911090447.GT788244@noisy.programming.kicks-ass.net

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Peter Zijlstra 2026-09-11 11:04:47 +02:00

parent fd73f4a665

commit b61b6f95d6

1 changed files with 2 additions and 2 deletions

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kernel/fork.c

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