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6f64e47783
The current logic checks if the name of the BTF type passed in
attach_btf_id starts with "bpf_lsm_", this is not sufficient as it also
allows attachment to non-LSM hooks like the very function that performs
this check, i.e. bpf_lsm_verify_prog.
In order to ensure that this verification logic allows attachment to
only LSM hooks, the LSM_HOOK definitions in lsm_hook_defs.h are used to
generate a BTF_ID set. Upon verification, the attach_btf_id of the
program being attached is checked for presence in this set.
Fixes: 9e4e01dfd3 ("bpf: lsm: Implement attach, detach and execution")
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201105230651.2621917-1-kpsingh@chromium.org
78 lines
1.9 KiB
C
78 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2020 Google LLC.
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*/
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#include <linux/filter.h>
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#include <linux/bpf.h>
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#include <linux/btf.h>
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#include <linux/lsm_hooks.h>
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#include <linux/bpf_lsm.h>
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#include <linux/kallsyms.h>
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#include <linux/bpf_verifier.h>
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#include <net/bpf_sk_storage.h>
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#include <linux/bpf_local_storage.h>
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#include <linux/btf_ids.h>
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/* For every LSM hook that allows attachment of BPF programs, declare a nop
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* function where a BPF program can be attached.
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*/
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#define LSM_HOOK(RET, DEFAULT, NAME, ...) \
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noinline RET bpf_lsm_##NAME(__VA_ARGS__) \
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{ \
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return DEFAULT; \
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}
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#include <linux/lsm_hook_defs.h>
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#undef LSM_HOOK
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#define LSM_HOOK(RET, DEFAULT, NAME, ...) BTF_ID(func, bpf_lsm_##NAME)
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BTF_SET_START(bpf_lsm_hooks)
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#include <linux/lsm_hook_defs.h>
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#undef LSM_HOOK
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BTF_SET_END(bpf_lsm_hooks)
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int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
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const struct bpf_prog *prog)
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{
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if (!prog->gpl_compatible) {
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bpf_log(vlog,
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"LSM programs must have a GPL compatible license\n");
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return -EINVAL;
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}
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if (!btf_id_set_contains(&bpf_lsm_hooks, prog->aux->attach_btf_id)) {
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bpf_log(vlog, "attach_btf_id %u points to wrong type name %s\n",
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prog->aux->attach_btf_id, prog->aux->attach_func_name);
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return -EINVAL;
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}
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return 0;
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}
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static const struct bpf_func_proto *
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bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
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{
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switch (func_id) {
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case BPF_FUNC_inode_storage_get:
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return &bpf_inode_storage_get_proto;
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case BPF_FUNC_inode_storage_delete:
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return &bpf_inode_storage_delete_proto;
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case BPF_FUNC_sk_storage_get:
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return &bpf_sk_storage_get_proto;
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case BPF_FUNC_sk_storage_delete:
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return &bpf_sk_storage_delete_proto;
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default:
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return tracing_prog_func_proto(func_id, prog);
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}
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}
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const struct bpf_prog_ops lsm_prog_ops = {
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};
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const struct bpf_verifier_ops lsm_verifier_ops = {
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.get_func_proto = bpf_lsm_func_proto,
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.is_valid_access = btf_ctx_access,
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};
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