bpf/verifier: add ARG_PTR_TO_UNINIT_MAP_VALUE

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>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e60fff4..0f8b863 100644 (file)
--- 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 3f93a54..d84c91a 100644 (file)
--- 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);