Chris Mason f35e3b5784 futex: Fix private hash use-after-free on resize ... poll_state_synchronize_rcu(mm->futex.phash.batches) is used by futex_ref_drop() to check that a grace period has passed since the current hash was published. This relies on batches referencing a grace period which started after the hash pointer was assigned. __futex_pivot_hash() sets mmph->batches before it replaces mmph->hash: scoped_guard(rcu) { mmph->batches = get_state_synchronize_rcu(); rcu_assign_pointer(mmph->hash, new); } The scoped_guard(rcu) doesn't stop new grace periods from starting, and if one starts between those two assignments, futex_ref_drop() can move forward while a reader still holds a pointer to the old hash. Fix things by setting mmph->batches after assigning mmph->hash. The scoped_guard(rcu) isn't needed, so let's drop that as well. Fixes: 56180dd20c ("futex: Use RCU-based per-CPU reference counting instead of rcuref_t") Assisted-by: kres Signed-off-by: Chris Mason <mason@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Link: https://patch.msgid.link/20261001135022.2220288-1-mason@kernel.org		2026-10-02 11:47:13 +02:00
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core.c	futex: Fix private hash use-after-free on resize	2026-10-02 11:47:13 +02:00
futex.h	futex: Optimize futex hash bucket access patterns	2026-06-11 13:41:24 +02:00
Makefile	futex: Convert to compiler context analysis	2026-03-16 13:16:48 +01:00
pi.c	futex: Provide rt_mutex_.*_schedule() equivalents for futex scheduling	2026-09-04 08:14:15 +02:00
requeue.c	futex: Prevent rcuwait use-after-free during requeue PI	2026-09-04 08:14:15 +02:00
syscalls.c	futex: Add support for unlocking robust futexes	2026-06-03 11:38:51 +02:00
waitwake.c	futex: Optimize futex hash bucket access patterns	2026-06-11 13:41:24 +02:00