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/arm64/mm/pgd.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 67 insertions(+) create mode 100644 arch/arm64/mm/pgd.c (limited to 'arch/arm64/mm/pgd.c') diff --git a/arch/arm64/mm/pgd.c b/arch/arm64/mm/pgd.c new file mode 100644 index 000000000..bf5110b91 --- /dev/null +++ b/arch/arm64/mm/pgd.c @@ -0,0 +1,67 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * PGD allocation/freeing + * + * Copyright (C) 2012 ARM Ltd. + * Author: Catalin Marinas + */ + +#include +#include +#include +#include + +#include +#include +#include + +static struct kmem_cache *pgd_cache __ro_after_init; + +static bool pgdir_is_page_size(void) +{ + if (PGD_SIZE == PAGE_SIZE) + return true; + if (CONFIG_PGTABLE_LEVELS == 4) + return !pgtable_l4_enabled(); + if (CONFIG_PGTABLE_LEVELS == 5) + return !pgtable_l5_enabled(); + return false; +} + +pgd_t *pgd_alloc(struct mm_struct *mm) +{ + gfp_t gfp = GFP_PGTABLE_USER; + + if (pgdir_is_page_size()) + return __pgd_alloc(mm, 0); + else + return kmem_cache_alloc(pgd_cache, gfp); +} + +void pgd_free(struct mm_struct *mm, pgd_t *pgd) +{ + if (pgdir_is_page_size()) + __pgd_free(mm, pgd); + else + kmem_cache_free(pgd_cache, pgd); +} + +void __init pgtable_cache_init(void) +{ + if (pgdir_is_page_size()) + return; + +#ifdef CONFIG_ARM64_PA_BITS_52 + /* + * With 52-bit physical addresses, the architecture requires the + * top-level table to be aligned to at least 64 bytes. + */ + BUILD_BUG_ON(!IS_ALIGNED(PGD_SIZE, 64)); +#endif + + /* + * Naturally aligned pgds required by the architecture. + */ + pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_SIZE, + SLAB_PANIC, NULL); +} -- cgit v1.3.1