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/arm/mm/pageattr.c | 111 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 111 insertions(+) create mode 100644 arch/arm/mm/pageattr.c (limited to 'arch/arm/mm/pageattr.c') diff --git a/arch/arm/mm/pageattr.c b/arch/arm/mm/pageattr.c new file mode 100644 index 000000000..064ad508c --- /dev/null +++ b/arch/arm/mm/pageattr.c @@ -0,0 +1,111 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (c) 2014, The Linux Foundation. All rights reserved. + */ +#include +#include + +#include +#include + +struct page_change_data { + pgprot_t set_mask; + pgprot_t clear_mask; +}; + +static int change_page_range(pte_t *ptep, unsigned long addr, void *data) +{ + struct page_change_data *cdata = data; + pte_t pte = *ptep; + + pte = clear_pte_bit(pte, cdata->clear_mask); + pte = set_pte_bit(pte, cdata->set_mask); + + set_pte_ext(ptep, pte, 0); + return 0; +} + +static bool range_in_range(unsigned long start, unsigned long size, + unsigned long range_start, unsigned long range_end) +{ + return start >= range_start && start < range_end && + size <= range_end - start; +} + +/* + * This function assumes that the range is mapped with PAGE_SIZE pages. + */ +static int __change_memory_common(unsigned long start, unsigned long size, + pgprot_t set_mask, pgprot_t clear_mask) +{ + struct page_change_data data; + int ret; + + data.set_mask = set_mask; + data.clear_mask = clear_mask; + + ret = apply_to_page_range(&init_mm, start, size, change_page_range, + &data); + + flush_tlb_kernel_range(start, start + size); + return ret; +} + +static int change_memory_common(unsigned long addr, int numpages, + pgprot_t set_mask, pgprot_t clear_mask) +{ + unsigned long start = addr & PAGE_MASK; + unsigned long end = PAGE_ALIGN(addr) + numpages * PAGE_SIZE; + unsigned long size = end - start; + + WARN_ON_ONCE(start != addr); + + if (!size) + return 0; + + if (!range_in_range(start, size, MODULES_VADDR, MODULES_END) && + !range_in_range(start, size, VMALLOC_START, VMALLOC_END)) + return -EINVAL; + + return __change_memory_common(start, size, set_mask, clear_mask); +} + +int set_memory_ro(unsigned long addr, int numpages) +{ + return change_memory_common(addr, numpages, + __pgprot(L_PTE_RDONLY), + __pgprot(0)); +} + +int set_memory_rw(unsigned long addr, int numpages) +{ + return change_memory_common(addr, numpages, + __pgprot(0), + __pgprot(L_PTE_RDONLY)); +} + +int set_memory_nx(unsigned long addr, int numpages) +{ + return change_memory_common(addr, numpages, + __pgprot(L_PTE_XN), + __pgprot(0)); +} + +int set_memory_x(unsigned long addr, int numpages) +{ + return change_memory_common(addr, numpages, + __pgprot(0), + __pgprot(L_PTE_XN)); +} + +int set_memory_valid(unsigned long addr, int numpages, int enable) +{ + if (enable) + return __change_memory_common(addr, PAGE_SIZE * numpages, + __pgprot(L_PTE_VALID), + __pgprot(0)); + else + return __change_memory_common(addr, PAGE_SIZE * numpages, + __pgprot(0), + __pgprot(L_PTE_VALID)); +} -- cgit v1.3.1