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/tlb.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 arch/arm/mm/tlb.c (limited to 'arch/arm/mm/tlb.c') diff --git a/arch/arm/mm/tlb.c b/arch/arm/mm/tlb.c new file mode 100644 index 000000000..423597931 --- /dev/null +++ b/arch/arm/mm/tlb.c @@ -0,0 +1,84 @@ +// SPDX-License-Identifier: GPL-2.0-only +// Copyright 2024 Google LLC +// Author: Ard Biesheuvel + +#include +#include + +#ifdef CONFIG_CPU_TLB_V4WT +void v4_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *); +void v4_flush_kern_tlb_range(unsigned long, unsigned long); + +struct cpu_tlb_fns v4_tlb_fns __initconst = { + .flush_user_range = v4_flush_user_tlb_range, + .flush_kern_range = v4_flush_kern_tlb_range, + .tlb_flags = v4_tlb_flags, +}; +#endif + +#ifdef CONFIG_CPU_TLB_V4WB +void v4wb_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *); +void v4wb_flush_kern_tlb_range(unsigned long, unsigned long); + +struct cpu_tlb_fns v4wb_tlb_fns __initconst = { + .flush_user_range = v4wb_flush_user_tlb_range, + .flush_kern_range = v4wb_flush_kern_tlb_range, + .tlb_flags = v4wb_tlb_flags, +}; +#endif + +#if defined(CONFIG_CPU_TLB_V4WBI) || defined(CONFIG_CPU_TLB_FEROCEON) +void v4wbi_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *); +void v4wbi_flush_kern_tlb_range(unsigned long, unsigned long); + +struct cpu_tlb_fns v4wbi_tlb_fns __initconst = { + .flush_user_range = v4wbi_flush_user_tlb_range, + .flush_kern_range = v4wbi_flush_kern_tlb_range, + .tlb_flags = v4wbi_tlb_flags, +}; +#endif + +#ifdef CONFIG_CPU_TLB_V6 +void v6wbi_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *); +void v6wbi_flush_kern_tlb_range(unsigned long, unsigned long); + +struct cpu_tlb_fns v6wbi_tlb_fns __initconst = { + .flush_user_range = v6wbi_flush_user_tlb_range, + .flush_kern_range = v6wbi_flush_kern_tlb_range, + .tlb_flags = v6wbi_tlb_flags, +}; +#endif + +#ifdef CONFIG_CPU_TLB_V7 +void v7wbi_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *); +void v7wbi_flush_kern_tlb_range(unsigned long, unsigned long); + +struct cpu_tlb_fns v7wbi_tlb_fns __initconst = { + .flush_user_range = v7wbi_flush_user_tlb_range, + .flush_kern_range = v7wbi_flush_kern_tlb_range, + .tlb_flags = IS_ENABLED(CONFIG_SMP) ? v7wbi_tlb_flags_smp + : v7wbi_tlb_flags_up, +}; + +#ifdef CONFIG_SMP_ON_UP +/* This will be run-time patched so the offset better be right */ +static_assert(offsetof(struct cpu_tlb_fns, tlb_flags) == 8); + +asm(" .pushsection \".alt.smp.init\", \"a\" \n" \ + " .align 2 \n" \ + " .long v7wbi_tlb_fns + 8 - . \n" \ + " .long " __stringify(v7wbi_tlb_flags_up) " \n" \ + " .popsection \n"); +#endif +#endif + +#ifdef CONFIG_CPU_TLB_FA +void fa_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *); +void fa_flush_kern_tlb_range(unsigned long, unsigned long); + +struct cpu_tlb_fns fa_tlb_fns __initconst = { + .flush_user_range = fa_flush_user_tlb_range, + .flush_kern_range = fa_flush_kern_tlb_range, + .tlb_flags = fa_tlb_flags, +}; +#endif -- cgit v1.3.1