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bpf: allow passing struct bpf_iter_<type> as kfunc arguments
There are potentially useful cases where a specific iterator type might need to be passed into some kfunc. So, in addition to existing bpf_iter_<type>_{new,next,destroy}() kfuncs, allow to pass iterator pointer to any kfunc. We employ "__iter" naming suffix for arguments that are meant to accept iterators. We also enforce that they accept PTR -> STRUCT btf_iter_<type> type chain and point to a valid initialized on-the-stack iterator state. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20240808232230.2848712-3-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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@ -7970,12 +7970,17 @@ static bool is_iter_destroy_kfunc(struct bpf_kfunc_call_arg_meta *meta)
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return meta->kfunc_flags & KF_ITER_DESTROY;
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}
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static bool is_kfunc_arg_iter(struct bpf_kfunc_call_arg_meta *meta, int arg)
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static bool is_kfunc_arg_iter(struct bpf_kfunc_call_arg_meta *meta, int arg_idx,
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const struct btf_param *arg)
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{
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/* btf_check_iter_kfuncs() guarantees that first argument of any iter
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* kfunc is iter state pointer
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*/
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return arg == 0 && is_iter_kfunc(meta);
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if (is_iter_kfunc(meta))
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return arg_idx == 0;
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/* iter passed as an argument to a generic kfunc */
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return btf_param_match_suffix(meta->btf, arg, "__iter");
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}
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static int process_iter_arg(struct bpf_verifier_env *env, int regno, int insn_idx,
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@ -7983,14 +7988,20 @@ static int process_iter_arg(struct bpf_verifier_env *env, int regno, int insn_id
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{
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struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno];
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const struct btf_type *t;
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const struct btf_param *arg;
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int spi, err, i, nr_slots;
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u32 btf_id;
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int spi, err, i, nr_slots, btf_id;
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/* btf_check_iter_kfuncs() ensures we don't need to validate anything here */
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arg = &btf_params(meta->func_proto)[0];
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t = btf_type_skip_modifiers(meta->btf, arg->type, NULL); /* PTR */
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t = btf_type_skip_modifiers(meta->btf, t->type, &btf_id); /* STRUCT */
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/* For iter_{new,next,destroy} functions, btf_check_iter_kfuncs()
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* ensures struct convention, so we wouldn't need to do any BTF
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* validation here. But given iter state can be passed as a parameter
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* to any kfunc, if arg has "__iter" suffix, we need to be a bit more
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* conservative here.
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*/
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btf_id = btf_check_iter_arg(meta->btf, meta->func_proto, regno - 1);
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if (btf_id < 0) {
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verbose(env, "expected valid iter pointer as arg #%d\n", regno);
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return -EINVAL;
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}
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t = btf_type_by_id(meta->btf, btf_id);
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nr_slots = t->size / BPF_REG_SIZE;
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if (is_iter_new_kfunc(meta)) {
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@ -8012,7 +8023,9 @@ static int process_iter_arg(struct bpf_verifier_env *env, int regno, int insn_id
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if (err)
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return err;
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} else {
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/* iter_next() or iter_destroy() expect initialized iter state*/
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/* iter_next() or iter_destroy(), as well as any kfunc
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* accepting iter argument, expect initialized iter state
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*/
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err = is_iter_reg_valid_init(env, reg, meta->btf, btf_id, nr_slots);
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switch (err) {
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case 0:
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@ -11382,7 +11395,7 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
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if (is_kfunc_arg_dynptr(meta->btf, &args[argno]))
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return KF_ARG_PTR_TO_DYNPTR;
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if (is_kfunc_arg_iter(meta, argno))
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if (is_kfunc_arg_iter(meta, argno, &args[argno]))
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return KF_ARG_PTR_TO_ITER;
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if (is_kfunc_arg_list_head(meta->btf, &args[argno]))
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