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/vmx-helper.c | 84 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 arch/powerpc/lib/vmx-helper.c (limited to 'arch/powerpc/lib/vmx-helper.c') diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c new file mode 100644 index 000000000..cc9fb72cb --- /dev/null +++ b/arch/powerpc/lib/vmx-helper.c @@ -0,0 +1,84 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * + * Copyright (C) IBM Corporation, 2011 + * + * Authors: Sukadev Bhattiprolu + * Anton Blanchard + */ +#include +#include +#include + +int enter_vmx_usercopy(void) +{ + if (in_interrupt()) + return 0; + + preempt_disable(); + /* + * We need to disable page faults as they can call schedule and + * thus make us lose the VMX context. So on page faults, we just + * fail which will cause a fallback to the normal non-vmx copy. + */ + pagefault_disable(); + + enable_kernel_altivec(); + + return 1; +} +EXPORT_SYMBOL(enter_vmx_usercopy); + +/* + * This function must return 0 because we tail call optimise when calling + * from __copy_tofrom_user_power7 which returns 0 on success. + */ +int exit_vmx_usercopy(void) +{ + disable_kernel_altivec(); + pagefault_enable(); + preempt_enable_no_resched(); + /* + * Must never explicitly call schedule (including preempt_enable()) + * while in a kuap-unlocked user copy, because the AMR register will + * not be saved and restored across context switch. However preempt + * kernels need to be preempted as soon as possible if need_resched is + * set and we are preemptible. The hack here is to schedule a + * decrementer to fire here and reschedule for us if necessary. + */ + if (need_resched()) + set_dec(1); + return 0; +} +EXPORT_SYMBOL(exit_vmx_usercopy); + +/* + * Can be called from kexec copy_page() path with MMU off. The kexec + * code sets preempt_count to HARDIRQ_OFFSET so we return early here. + * Since in_interrupt() is always inline, __no_sanitize_address on this + * function is sufficient to avoid KASAN shadow memory accesses in real + * mode. + */ +int __no_sanitize_address enter_vmx_ops(void) +{ + if (in_interrupt()) + return 0; + + preempt_disable(); + + enable_kernel_altivec(); + + return 1; +} + +/* + * All calls to this function will be optimised into tail calls. We are + * passed a pointer to the destination which we return as required by a + * memcpy implementation. + */ +void *exit_vmx_ops(void *dest) +{ + disable_kernel_altivec(); + preempt_enable(); + return dest; +} -- cgit v1.3.1