Add ability to mark arg:trusted arguments with optional arg:maybe_null
tag to mark is as PTR_TO_BTF_ID_OR_NULL variant, which will allow
callers to pass NULL, and subsequently will force global subprog's code
to do NULL check. This allows to have "optional" PTR_TO_BTF_ID values
passed into global subprogs.
For now arg:maybe_null cannot be combined with anything else.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
kernel/bpf/btf.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ed7a05815984..270804ece93c 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7056,6 +7056,7 @@ enum btf_arg_tag {
ARG_TAG_CTX = 0x1,
ARG_TAG_NONNULL = 0x2,
ARG_TAG_TRUSTED = 0x4,
+ ARG_TAG_MAYBE_NULL = 0x8,
};
/* Process BTF of a function to produce high-level expectation of function
@@ -7161,6 +7162,8 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog)
tags |= ARG_TAG_TRUSTED;
} else if (strcmp(tag, "nonnull") == 0) {
tags |= ARG_TAG_NONNULL;
+ } else if (strcmp(tag, "maybe_null") == 0) {
+ tags |= ARG_TAG_MAYBE_NULL;
} else {
bpf_log(log, "arg#%d has unsupported set of tags\n", i);
return -EOPNOTSUPP;
@@ -7210,12 +7213,19 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog)
return kern_type_id;
sub->args[i].arg_type = ARG_PTR_TO_BTF_ID | PTR_TRUSTED;
+ if (tags & ARG_TAG_MAYBE_NULL)
+ sub->args[i].arg_type |= PTR_MAYBE_NULL;
sub->args[i].btf_id = kern_type_id;
continue;
}
if (is_global) { /* generic user data pointer */
u32 mem_size;
+ if (tags & ARG_TAG_MAYBE_NULL) {
+ bpf_log(log, "arg#%d has invalid combination of tags\n", i);
+ return -EINVAL;
+ }
+
t = btf_type_skip_modifiers(btf, t->type, NULL);
ref_t = btf_resolve_size(btf, t, &mem_size);
if (IS_ERR(ref_t)) {
--
2.34.1
