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bpf: add arg:nullable tag to be combined with trusted pointers

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Add ability to mark arg:trusted arguments with optional arg:nullable
tag to mark it 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:nullable cannot be combined with anything else.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240130000648.2144827-3-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2024-01-29 16:06:46 -08:00 committed by Alexei Starovoitov
parent e2b3c4ff5d
commit 8f2b44cd9d
1 changed files with 10 additions and 0 deletions
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10
kernel/bpf/btf.c
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@ -7056,6 +7056,7 @@ enum btf_arg_tag {
ARG_TAG_CTX = 0x1,
ARG_TAG_NONNULL = 0x2,
ARG_TAG_TRUSTED = 0x4,
ARG_TAG_NULLABLE = 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, "nullable") == 0) {
tags |= ARG_TAG_NULLABLE;
} 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_NULLABLE)
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_NULLABLE) {
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)) {