From 33ff9823c569f3aceb071071914919177a6bed6a Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 13 Apr 2016 00:10:50 +0200 Subject: [PATCH] bpf, verifier: add bpf_call_arg_meta for passing meta data Currently, when the verifier checks calls in check_call() function, we call check_func_arg() for all 5 arguments e.g. to make sure expected types are correct. In some cases, we collect meta data (here: map pointer) to perform additional checks such as checking stack boundary on key/value sizes for subsequent arguments. As we're going to extend the meta data, add a generic struct bpf_call_arg_meta that we can use for passing into check_func_arg(). Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/verifier.c | 40 +++++++++++++++++++++++----------------- 1 file changed, 23 insertions(+), 17 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 6c5d7cd4cb0e..202f8f738542 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -205,6 +205,10 @@ struct verifier_env { #define BPF_COMPLEXITY_LIMIT_INSNS 65536 #define BPF_COMPLEXITY_LIMIT_STACK 1024 +struct bpf_call_arg_meta { + struct bpf_map *map_ptr; +}; + /* verbose verifier prints what it's seeing * bpf_check() is called under lock, so no race to access these global vars */ @@ -822,7 +826,8 @@ static int check_stack_boundary(struct verifier_env *env, int regno, } static int check_func_arg(struct verifier_env *env, u32 regno, - enum bpf_arg_type arg_type, struct bpf_map **mapp) + enum bpf_arg_type arg_type, + struct bpf_call_arg_meta *meta) { struct reg_state *reg = env->cur_state.regs + regno; enum bpf_reg_type expected_type; @@ -875,14 +880,13 @@ static int check_func_arg(struct verifier_env *env, u32 regno, if (arg_type == ARG_CONST_MAP_PTR) { /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ - *mapp = reg->map_ptr; - + meta->map_ptr = reg->map_ptr; } else if (arg_type == ARG_PTR_TO_MAP_KEY) { /* bpf_map_xxx(..., map_ptr, ..., key) call: * check that [key, key + map->key_size) are within * stack limits and initialized */ - if (!*mapp) { + if (!meta->map_ptr) { /* in function declaration map_ptr must come before * map_key, so that it's verified and known before * we have to check map_key here. Otherwise it means @@ -891,19 +895,19 @@ static int check_func_arg(struct verifier_env *env, u32 regno, verbose("invalid map_ptr to access map->key\n"); return -EACCES; } - err = check_stack_boundary(env, regno, (*mapp)->key_size, + err = check_stack_boundary(env, regno, meta->map_ptr->key_size, false); } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { /* bpf_map_xxx(..., map_ptr, ..., value) call: * check [value, value + map->value_size) validity */ - if (!*mapp) { + if (!meta->map_ptr) { /* kernel subsystem misconfigured verifier */ verbose("invalid map_ptr to access map->value\n"); return -EACCES; } - err = check_stack_boundary(env, regno, (*mapp)->value_size, - false); + err = check_stack_boundary(env, regno, + meta->map_ptr->value_size, false); } else if (arg_type == ARG_CONST_STACK_SIZE || arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) { bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO); @@ -954,8 +958,8 @@ static int check_call(struct verifier_env *env, int func_id) struct verifier_state *state = &env->cur_state; const struct bpf_func_proto *fn = NULL; struct reg_state *regs = state->regs; - struct bpf_map *map = NULL; struct reg_state *reg; + struct bpf_call_arg_meta meta; int i, err; /* find function prototype */ @@ -978,20 +982,22 @@ static int check_call(struct verifier_env *env, int func_id) return -EINVAL; } + memset(&meta, 0, sizeof(meta)); + /* check args */ - err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &map); + err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta); if (err) return err; - err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &map); + err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta); if (err) return err; - err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &map); + err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta); if (err) return err; - err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &map); + err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta); if (err) return err; - err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &map); + err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta); if (err) return err; @@ -1013,18 +1019,18 @@ static int check_call(struct verifier_env *env, int func_id) * can check 'value_size' boundary of memory access * to map element returned from bpf_map_lookup_elem() */ - if (map == NULL) { + if (meta.map_ptr == NULL) { verbose("kernel subsystem misconfigured verifier\n"); return -EINVAL; } - regs[BPF_REG_0].map_ptr = map; + regs[BPF_REG_0].map_ptr = meta.map_ptr; } else { verbose("unknown return type %d of func %d\n", fn->ret_type, func_id); return -EINVAL; } - err = check_map_func_compatibility(map, func_id); + err = check_map_func_compatibility(meta.map_ptr, func_id); if (err) return err;