From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- arch/powerpc/lib/locks.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 arch/powerpc/lib/locks.c (limited to 'arch/powerpc/lib/locks.c') diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c new file mode 100644 index 000000000..04165b7a1 --- /dev/null +++ b/arch/powerpc/lib/locks.c @@ -0,0 +1,65 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Spin and read/write lock operations. + * + * Copyright (C) 2001-2004 Paul Mackerras , IBM + * Copyright (C) 2001 Anton Blanchard , IBM + * Copyright (C) 2002 Dave Engebretsen , IBM + * Rework to support virtual processors + */ + +#include +#include +#include +#include + +/* waiting for a spinlock... */ +#if defined(CONFIG_PPC_SPLPAR) +#include +#include + +void splpar_spin_yield(arch_spinlock_t *lock) +{ + unsigned int lock_value, holder_cpu, yield_count; + + lock_value = lock->slock; + if (lock_value == 0) + return; + holder_cpu = lock_value & 0xffff; + BUG_ON(holder_cpu >= NR_CPUS); + + yield_count = yield_count_of(holder_cpu); + if ((yield_count & 1) == 0) + return; /* virtual cpu is currently running */ + rmb(); + if (lock->slock != lock_value) + return; /* something has changed */ + yield_to_preempted(holder_cpu, yield_count); +} +EXPORT_SYMBOL_GPL(splpar_spin_yield); + +/* + * Waiting for a read lock or a write lock on a rwlock... + * This turns out to be the same for read and write locks, since + * we only know the holder if it is write-locked. + */ +void splpar_rw_yield(arch_rwlock_t *rw) +{ + int lock_value; + unsigned int holder_cpu, yield_count; + + lock_value = rw->lock; + if (lock_value >= 0) + return; /* no write lock at present */ + holder_cpu = lock_value & 0xffff; + BUG_ON(holder_cpu >= NR_CPUS); + + yield_count = yield_count_of(holder_cpu); + if ((yield_count & 1) == 0) + return; /* virtual cpu is currently running */ + rmb(); + if (rw->lock != lock_value) + return; /* something has changed */ + yield_to_preempted(holder_cpu, yield_count); +} +#endif -- cgit v1.3.1