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>

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

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);