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/x86/hyperv/nested.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 130 insertions(+) create mode 100644 arch/x86/hyperv/nested.c (limited to 'arch/x86/hyperv/nested.c') diff --git a/arch/x86/hyperv/nested.c b/arch/x86/hyperv/nested.c new file mode 100644 index 000000000..8ccbb7c4f --- /dev/null +++ b/arch/x86/hyperv/nested.c @@ -0,0 +1,130 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Hyper-V nested virtualization code. + * + * Copyright (C) 2018, Microsoft, Inc. + * + * Author : Lan Tianyu + */ +#define pr_fmt(fmt) "Hyper-V: " fmt + + +#include +#include +#include +#include +#include + +#include + +int hyperv_flush_guest_mapping(u64 as) +{ + struct hv_guest_mapping_flush *flush; + u64 status; + unsigned long flags; + int ret = -ENOTSUPP; + + if (!hv_hypercall_pg) + goto fault; + + local_irq_save(flags); + + flush = *this_cpu_ptr(hyperv_pcpu_input_arg); + + if (unlikely(!flush)) { + local_irq_restore(flags); + goto fault; + } + + flush->address_space = as; + flush->flags = 0; + + status = hv_do_hypercall(HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE, + flush, NULL); + local_irq_restore(flags); + + if (hv_result_success(status)) + ret = 0; + +fault: + trace_hyperv_nested_flush_guest_mapping(as, ret); + return ret; +} +EXPORT_SYMBOL_GPL(hyperv_flush_guest_mapping); + +int hyperv_fill_flush_guest_mapping_list( + struct hv_guest_mapping_flush_list *flush, + u64 start_gfn, u64 pages) +{ + u64 cur = start_gfn; + u64 additional_pages; + int gpa_n = 0; + + do { + /* + * If flush requests exceed max flush count, go back to + * flush tlbs without range. + */ + if (gpa_n >= HV_MAX_FLUSH_REP_COUNT) + return -ENOSPC; + + additional_pages = min_t(u64, pages, HV_MAX_FLUSH_PAGES) - 1; + + flush->gpa_list[gpa_n].page.additional_pages = additional_pages; + flush->gpa_list[gpa_n].page.largepage = false; + flush->gpa_list[gpa_n].page.basepfn = cur; + + pages -= additional_pages + 1; + cur += additional_pages + 1; + gpa_n++; + } while (pages > 0); + + return gpa_n; +} +EXPORT_SYMBOL_GPL(hyperv_fill_flush_guest_mapping_list); + +int hyperv_flush_guest_mapping_range(u64 as, + hyperv_fill_flush_list_func fill_flush_list_func, void *data) +{ + struct hv_guest_mapping_flush_list *flush; + u64 status; + unsigned long flags; + int ret = -ENOTSUPP; + int gpa_n = 0; + + if (!hv_hypercall_pg || !fill_flush_list_func) + goto fault; + + local_irq_save(flags); + + flush = *this_cpu_ptr(hyperv_pcpu_input_arg); + + if (unlikely(!flush)) { + local_irq_restore(flags); + goto fault; + } + + flush->address_space = as; + flush->flags = 0; + + gpa_n = fill_flush_list_func(flush, data); + if (gpa_n < 0) { + local_irq_restore(flags); + goto fault; + } + + status = hv_do_rep_hypercall(HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST, + gpa_n, 0, flush, NULL); + + local_irq_restore(flags); + + if (hv_result_success(status)) + ret = 0; + else + ret = hv_result(status); +fault: + trace_hyperv_nested_flush_guest_mapping_range(as, ret); + return ret; +} +EXPORT_SYMBOL_GPL(hyperv_flush_guest_mapping_range); -- cgit v1.3.1