[PATCH bpf-next v3 3/7] bpf/verifier: add ARG_PTR_TO_UNINIT_MAP_VALUE

Mauricio Vasquez B
2018-10-18T21:17:43Z

ARG_PTR_TO_UNINIT_MAP_VALUE argument is a pointer to a memory zone
used to save the value of a map. Basically the same as
ARG_PTR_TO_UNINIT_MEM, but the size has not be passed as an extra
argument.

This will be used in the following patch that implements some new
helpers that receive a pointer to be filled with a map value.

Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it>
Acked-by: Song Liu <songliubraving@fb.com>
---
include/linux/bpf.h | 1 +
kernel/bpf/verifier.c | 9 ++++++---
2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e60fff48288b..0f8b863e0229 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -138,6 +138,7 @@ enum bpf_arg_type {
ARG_CONST_MAP_PTR, /* const argument used as pointer to bpf_map */
ARG_PTR_TO_MAP_KEY, /* pointer to stack used as map key */
ARG_PTR_TO_MAP_VALUE, /* pointer to stack used as map value */
+ ARG_PTR_TO_UNINIT_MAP_VALUE, /* pointer to valid memory used to store a map value */

/* the following constraints used to prototype bpf_memcmp() and other
* functions that access data on eBPF program stack
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3f93a548a642..d84c91ac3b70 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2117,7 +2117,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
}

if (arg_type == ARG_PTR_TO_MAP_KEY ||
- arg_type == ARG_PTR_TO_MAP_VALUE) {
+ arg_type == ARG_PTR_TO_MAP_VALUE ||
+ arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
expected_type = PTR_TO_STACK;
if (!type_is_pkt_pointer(type) && type != PTR_TO_MAP_VALUE &&
type != expected_type)
@@ -2187,7 +2188,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
err = check_helper_mem_access(env, regno,
meta->map_ptr->key_size, false,
NULL);
- } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
+ } else if (arg_type == ARG_PTR_TO_MAP_VALUE ||
+ arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
/* bpf_map_xxx(..., map_ptr, ..., value) call:
* check [value, value + map->value_size) validity
*/
@@ -2196,9 +2198,10 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
verbose(env, "invalid map_ptr to access map->value\n");
return -EACCES;
}
+ meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE);
err = check_helper_mem_access(env, regno,
meta->map_ptr->value_size, false,
- NULL);
+ meta);
} else if (arg_type_is_mem_size(arg_type)) {
bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);