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 --- samples/bpf/sampleip_kern.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) create mode 100644 samples/bpf/sampleip_kern.c (limited to 'samples/bpf/sampleip_kern.c') diff --git a/samples/bpf/sampleip_kern.c b/samples/bpf/sampleip_kern.c new file mode 100644 index 000000000..a3f8a3998 --- /dev/null +++ b/samples/bpf/sampleip_kern.c @@ -0,0 +1,38 @@ +/* Copyright 2016 Netflix, Inc. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + */ +#include +#include +#include +#include +#include + +#define MAX_IPS 8192 + +struct { + __uint(type, BPF_MAP_TYPE_HASH); + __type(key, u64); + __type(value, u32); + __uint(max_entries, MAX_IPS); +} ip_map SEC(".maps"); + +SEC("perf_event") +int do_sample(struct bpf_perf_event_data *ctx) +{ + u64 ip; + u32 *value, init_val = 1; + + ip = PT_REGS_IP(&ctx->regs); + value = bpf_map_lookup_elem(&ip_map, &ip); + if (value) + *value += 1; + else + /* E2BIG not tested for this example only */ + bpf_map_update_elem(&ip_map, &ip, &init_val, BPF_NOEXIST); + + return 0; +} +char _license[] SEC("license") = "GPL"; -- cgit v1.3.1