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/mm/pgprot.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 arch/x86/mm/pgprot.c (limited to 'arch/x86/mm/pgprot.c') diff --git a/arch/x86/mm/pgprot.c b/arch/x86/mm/pgprot.c new file mode 100644 index 000000000..dc1afd5c8 --- /dev/null +++ b/arch/x86/mm/pgprot.c @@ -0,0 +1,63 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include + +static pgprot_t protection_map[16] __ro_after_init = { + [VM_NONE] = PAGE_NONE, + [VM_READ] = PAGE_READONLY, + [VM_WRITE] = PAGE_COPY, + [VM_WRITE | VM_READ] = PAGE_COPY, + [VM_EXEC] = PAGE_READONLY_EXEC, + [VM_EXEC | VM_READ] = PAGE_READONLY_EXEC, + [VM_EXEC | VM_WRITE] = PAGE_COPY_EXEC, + [VM_EXEC | VM_WRITE | VM_READ] = PAGE_COPY_EXEC, + [VM_SHARED] = PAGE_NONE, + [VM_SHARED | VM_READ] = PAGE_READONLY, + [VM_SHARED | VM_WRITE] = PAGE_SHARED, + [VM_SHARED | VM_WRITE | VM_READ] = PAGE_SHARED, + [VM_SHARED | VM_EXEC] = PAGE_READONLY_EXEC, + [VM_SHARED | VM_EXEC | VM_READ] = PAGE_READONLY_EXEC, + [VM_SHARED | VM_EXEC | VM_WRITE] = PAGE_SHARED_EXEC, + [VM_SHARED | VM_EXEC | VM_WRITE | VM_READ] = PAGE_SHARED_EXEC +}; + +void add_encrypt_protection_map(void) +{ + unsigned int i; + + for (i = 0; i < ARRAY_SIZE(protection_map); i++) + protection_map[i] = pgprot_encrypted(protection_map[i]); +} + +pgprot_t vm_get_page_prot(vm_flags_t vm_flags) +{ + unsigned long val = pgprot_val(protection_map[vm_flags & + (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]); + +#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS + /* + * Take the 4 protection key bits out of the vma->vm_flags value and + * turn them in to the bits that we can put in to a pte. + * + * Only override these if Protection Keys are available (which is only + * on 64-bit). + */ + if (vm_flags & VM_PKEY_BIT0) + val |= _PAGE_PKEY_BIT0; + if (vm_flags & VM_PKEY_BIT1) + val |= _PAGE_PKEY_BIT1; + if (vm_flags & VM_PKEY_BIT2) + val |= _PAGE_PKEY_BIT2; + if (vm_flags & VM_PKEY_BIT3) + val |= _PAGE_PKEY_BIT3; +#endif + + val = __sme_set(val); + if (val & _PAGE_PRESENT) + val &= __supported_pte_mask; + return __pgprot(val); +} +EXPORT_SYMBOL(vm_get_page_prot); -- cgit v1.3.1