diff options
Diffstat (limited to 'kernel/bpf/verifier.c')
-rw-r--r-- | kernel/bpf/verifier.c | 113 |
1 files changed, 105 insertions, 8 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index ec767ae08c2b..ec3f22312516 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2457,6 +2457,68 @@ static int add_subprog(struct bpf_verifier_env *env, int off) return env->subprog_cnt - 1; } +static int bpf_find_exception_callback_insn_off(struct bpf_verifier_env *env) +{ + struct bpf_prog_aux *aux = env->prog->aux; + struct btf *btf = aux->btf; + const struct btf_type *t; + u32 main_btf_id, id; + const char *name; + int ret, i; + + /* Non-zero func_info_cnt implies valid btf */ + if (!aux->func_info_cnt) + return 0; + main_btf_id = aux->func_info[0].type_id; + + t = btf_type_by_id(btf, main_btf_id); + if (!t) { + verbose(env, "invalid btf id for main subprog in func_info\n"); + return -EINVAL; + } + + name = btf_find_decl_tag_value(btf, t, -1, "exception_callback:"); + if (IS_ERR(name)) { + ret = PTR_ERR(name); + /* If there is no tag present, there is no exception callback */ + if (ret == -ENOENT) + ret = 0; + else if (ret == -EEXIST) + verbose(env, "multiple exception callback tags for main subprog\n"); + return ret; + } + + ret = btf_find_by_name_kind(btf, name, BTF_KIND_FUNC); + if (ret < 0) { + verbose(env, "exception callback '%s' could not be found in BTF\n", name); + return ret; + } + id = ret; + t = btf_type_by_id(btf, id); + if (btf_func_linkage(t) != BTF_FUNC_GLOBAL) { + verbose(env, "exception callback '%s' must have global linkage\n", name); + return -EINVAL; + } + ret = 0; + for (i = 0; i < aux->func_info_cnt; i++) { + if (aux->func_info[i].type_id != id) + continue; + ret = aux->func_info[i].insn_off; + /* Further func_info and subprog checks will also happen + * later, so assume this is the right insn_off for now. + */ + if (!ret) { + verbose(env, "invalid exception callback insn_off in func_info: 0\n"); + ret = -EINVAL; + } + } + if (!ret) { + verbose(env, "exception callback type id not found in func_info\n"); + ret = -EINVAL; + } + return ret; +} + #define MAX_KFUNC_DESCS 256 #define MAX_KFUNC_BTFS 256 @@ -2796,8 +2858,8 @@ bpf_jit_find_kfunc_model(const struct bpf_prog *prog, static int add_subprog_and_kfunc(struct bpf_verifier_env *env) { struct bpf_subprog_info *subprog = env->subprog_info; + int i, ret, insn_cnt = env->prog->len, ex_cb_insn; struct bpf_insn *insn = env->prog->insnsi; - int i, ret, insn_cnt = env->prog->len; /* Add entry function. */ ret = add_subprog(env, 0); @@ -2823,6 +2885,26 @@ static int add_subprog_and_kfunc(struct bpf_verifier_env *env) return ret; } + ret = bpf_find_exception_callback_insn_off(env); + if (ret < 0) + return ret; + ex_cb_insn = ret; + + /* If ex_cb_insn > 0, this means that the main program has a subprog + * marked using BTF decl tag to serve as the exception callback. + */ + if (ex_cb_insn) { + ret = add_subprog(env, ex_cb_insn); + if (ret < 0) + return ret; + for (i = 1; i < env->subprog_cnt; i++) { + if (env->subprog_info[i].start != ex_cb_insn) + continue; + env->exception_callback_subprog = i; + break; + } + } + /* Add a fake 'exit' subprog which could simplify subprog iteration * logic. 'subprog_cnt' should not be increased. */ @@ -5707,6 +5789,10 @@ continue_func: /* async callbacks don't increase bpf prog stack size unless called directly */ if (!bpf_pseudo_call(insn + i)) continue; + if (subprog[sidx].is_exception_cb) { + verbose(env, "insn %d cannot call exception cb directly\n", i); + return -EINVAL; + } } i = next_insn; idx = sidx; @@ -5728,8 +5814,13 @@ continue_func: * tail call counter throughout bpf2bpf calls combined with tailcalls */ if (tail_call_reachable) - for (j = 0; j < frame; j++) + for (j = 0; j < frame; j++) { + if (subprog[ret_prog[j]].is_exception_cb) { + verbose(env, "cannot tail call within exception cb\n"); + return -EINVAL; + } subprog[ret_prog[j]].tail_call_reachable = true; + } if (subprog[0].tail_call_reachable) env->prog->aux->tail_call_reachable = true; @@ -14630,7 +14721,7 @@ static int check_return_code(struct bpf_verifier_env *env) const bool is_subprog = frame->subprogno; /* LSM and struct_ops func-ptr's return type could be "void" */ - if (!is_subprog) { + if (!is_subprog || frame->in_exception_callback_fn) { switch (prog_type) { case BPF_PROG_TYPE_LSM: if (prog->expected_attach_type == BPF_LSM_CGROUP) @@ -14678,7 +14769,7 @@ static int check_return_code(struct bpf_verifier_env *env) return 0; } - if (is_subprog) { + if (is_subprog && !frame->in_exception_callback_fn) { if (reg->type != SCALAR_VALUE) { verbose(env, "At subprogram exit the register R0 is not a scalar value (%s)\n", reg_type_str(env, reg->type)); @@ -19334,7 +19425,7 @@ static void free_states(struct bpf_verifier_env *env) } } -static int do_check_common(struct bpf_verifier_env *env, int subprog) +static int do_check_common(struct bpf_verifier_env *env, int subprog, bool is_ex_cb) { bool pop_log = !(env->log.level & BPF_LOG_LEVEL2); struct bpf_verifier_state *state; @@ -19365,7 +19456,7 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog) regs = state->frame[state->curframe]->regs; if (subprog || env->prog->type == BPF_PROG_TYPE_EXT) { - ret = btf_prepare_func_args(env, subprog, regs); + ret = btf_prepare_func_args(env, subprog, regs, is_ex_cb); if (ret) goto out; for (i = BPF_REG_1; i <= BPF_REG_5; i++) { @@ -19381,6 +19472,12 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog) regs[i].id = ++env->id_gen; } } + if (is_ex_cb) { + state->frame[0]->in_exception_callback_fn = true; + env->subprog_info[subprog].is_cb = true; + env->subprog_info[subprog].is_async_cb = true; + env->subprog_info[subprog].is_exception_cb = true; + } } else { /* 1st arg to a function */ regs[BPF_REG_1].type = PTR_TO_CTX; @@ -19445,7 +19542,7 @@ static int do_check_subprogs(struct bpf_verifier_env *env) continue; env->insn_idx = env->subprog_info[i].start; WARN_ON_ONCE(env->insn_idx == 0); - ret = do_check_common(env, i); + ret = do_check_common(env, i, env->exception_callback_subprog == i); if (ret) { return ret; } else if (env->log.level & BPF_LOG_LEVEL) { @@ -19462,7 +19559,7 @@ static int do_check_main(struct bpf_verifier_env *env) int ret; env->insn_idx = 0; - ret = do_check_common(env, 0); + ret = do_check_common(env, 0, false); if (!ret) env->prog->aux->stack_depth = env->subprog_info[0].stack_depth; return ret; |