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 --- security/bpf/hooks.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 security/bpf/hooks.c (limited to 'security/bpf/hooks.c') diff --git a/security/bpf/hooks.c b/security/bpf/hooks.c new file mode 100644 index 000000000..7b98f5d1e --- /dev/null +++ b/security/bpf/hooks.c @@ -0,0 +1,42 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Copyright (C) 2020 Google LLC. + */ +#include +#include +#include + +bool bpf_lsm_initialized __ro_after_init; + +static struct security_hook_list bpf_lsm_hooks[] __ro_after_init = { + #define LSM_HOOK(RET, DEFAULT, NAME, ...) \ + LSM_HOOK_INIT(NAME, bpf_lsm_##NAME), + #include + #undef LSM_HOOK + LSM_HOOK_INIT(inode_free_security, bpf_inode_storage_free), +}; + +static const struct lsm_id bpf_lsmid = { + .name = "bpf", + .id = LSM_ID_BPF, +}; + +static int __init bpf_lsm_init(void) +{ + security_add_hooks(bpf_lsm_hooks, ARRAY_SIZE(bpf_lsm_hooks), + &bpf_lsmid); + bpf_lsm_initialized = true; + pr_info("LSM support for eBPF active\n"); + return 0; +} + +struct lsm_blob_sizes bpf_lsm_blob_sizes __ro_after_init = { + .lbs_inode = sizeof(struct bpf_storage_blob), +}; + +DEFINE_LSM(bpf) = { + .id = &bpf_lsmid, + .init = bpf_lsm_init, + .blobs = &bpf_lsm_blob_sizes +}; -- cgit v1.3.1