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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 <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2016-04-13 00:10:50 +02:00 committed by David S. Miller
parent 486bdee013
commit 33ff9823c5
1 changed files with 23 additions and 17 deletions
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40
kernel/bpf/verifier.c
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@ -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;