diff options
| author | Yafang Shao <laoar.shao@gmail.com> | 2023-07-13 02:56:39 +0000 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-07-13 16:24:29 -0700 |
| commit | 7ce4dc3e4a9d954c8a1fb483c7a527e9b060b860 (patch) | |
| tree | 813bb3f4b15f5eb7548a4f6740bb8826a12b592a | |
| parent | f892cac2371447b3a26dad117c7bcdf2c93215e1 (diff) | |
bpf: Fix an error around PTR_UNTRUSTED
Per discussion with Alexei, the PTR_UNTRUSTED flag should not been
cleared when we start to walk a new struct, because the struct in
question may be a struct nested in a union. We should also check and set
this flag before we walk its each member, in case itself is a union.
We will clear this flag if the field is BTF_TYPE_SAFE_RCU_OR_NULL.
Fixes: 6fcd486b3a0a ("bpf: Refactor RCU enforcement in the verifier.")
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20230713025642.27477-2-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | kernel/bpf/btf.c | 20 | ||||
| -rw-r--r-- | kernel/bpf/verifier.c | 5 |
2 files changed, 14 insertions, 11 deletions
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 3dd47451f097..fae6fc24a845 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6133,7 +6133,6 @@ static int btf_struct_walk(struct bpf_verifier_log *log, const struct btf *btf, const char *tname, *mname, *tag_value; u32 vlen, elem_id, mid; - *flag = 0; again: if (btf_type_is_modifier(t)) t = btf_type_skip_modifiers(btf, t->type, NULL); @@ -6144,6 +6143,14 @@ again: } vlen = btf_type_vlen(t); + if (BTF_INFO_KIND(t->info) == BTF_KIND_UNION && vlen != 1 && !(*flag & PTR_UNTRUSTED)) + /* + * walking unions yields untrusted pointers + * with exception of __bpf_md_ptr and other + * unions with a single member + */ + *flag |= PTR_UNTRUSTED; + if (off + size > t->size) { /* If the last element is a variable size array, we may * need to relax the rule. @@ -6304,15 +6311,6 @@ error: * of this field or inside of this struct */ if (btf_type_is_struct(mtype)) { - if (BTF_INFO_KIND(mtype->info) == BTF_KIND_UNION && - btf_type_vlen(mtype) != 1) - /* - * walking unions yields untrusted pointers - * with exception of __bpf_md_ptr and other - * unions with a single member - */ - *flag |= PTR_UNTRUSTED; - /* our field must be inside that union or struct */ t = mtype; @@ -6478,7 +6476,7 @@ bool btf_struct_ids_match(struct bpf_verifier_log *log, bool strict) { const struct btf_type *type; - enum bpf_type_flag flag; + enum bpf_type_flag flag = 0; int err; /* Are we already done? */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 81a93eeac7a0..584eb34dce8a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6067,6 +6067,11 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, type_is_rcu_or_null(env, reg, field_name, btf_id)) { /* __rcu tagged pointers can be NULL */ flag |= MEM_RCU | PTR_MAYBE_NULL; + + /* We always trust them */ + if (type_is_rcu_or_null(env, reg, field_name, btf_id) && + flag & PTR_UNTRUSTED) + flag &= ~PTR_UNTRUSTED; } else if (flag & (MEM_PERCPU | MEM_USER)) { /* keep as-is */ } else { |