bpf: Set meta->raw_mode for pointers close to use

If we encounter a pointer to memory, we set meta->raw_mode depending on the type of memory we point at. What isn't obvious is that this information is only used when the next memory size argument is encountered. Move the assignment closer to where it's used, and add a comment that explains what is going on. Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Martin KaFai Lau <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
jix · Sep 21, 2020 · a2bbe7c · a2bbe7c
1 parent feec704
commit a2bbe7c
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
@@ -4067,7 +4067,6 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			 type != PTR_TO_RDWR_BUF &&
 			 type != expected_type)
 			goto err_type;
-		meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM;
 	} else if (arg_type_is_alloc_mem_ptr(arg_type)) {
 		expected_type = PTR_TO_MEM;
 		if (register_is_null(reg) &&
@@ -4156,6 +4155,11 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		err = check_helper_mem_access(env, regno,
 					      meta->map_ptr->value_size, false,
 					      meta);
+	} else if (arg_type_is_mem_ptr(arg_type)) {
+		/* The access to this pointer is only checked when we hit the
+		 * next is_mem_size argument below.
+		 */
+		meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MEM);
 	} else if (arg_type_is_mem_size(arg_type)) {
 		bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);