From: Amery Hung <ameryhung@gmail.com>
To: bpf@vger.kernel.org
Cc: alexei.starovoitov@gmail.com, andrii@kernel.org,
daniel@iogearbox.net, eddyz87@gmail.com, memxor@gmail.com,
ameryhung@gmail.com, kernel-team@meta.com
Subject: [PATCH bpf-next v2 11/23] bpf: Set MEM_RCU when generating kfunc argument types
Date: Fri, 11 Sep 2026 15:04:03 -0700 [thread overview]
Message-ID: <20260911220415.1396439-12-ameryhung@gmail.com> (raw)
In-Reply-To: <20260911220415.1396439-1-ameryhung@gmail.com>
The BTF ID argument of a kfunc has to be referenced or trusted unless
the kfunc is KF_RCU, in which case an RCU-protected pointer is accepted
too. check_kfunc_args() reads that off meta->kfunc_flags on every
verification of the call, which is the last thing keeping the argument
policy of ARG_PTR_TO_BTF_ID out of the generated prototype.
Set MEM_RCU in get_kfunc_arg_type() for ARG_PTR_TO_BTF_ID arguments of
KF_RCU kfuncs, the way it already sets OBJ_RELEASE for release
arguments, and test the generated flag instead. MEM_RCU represents the
KF_RCU relaxation applied by the ARG_PTR_TO_BTF_ID trust check; other
argument kinds have their own provenance requirements.
No functional change intended.
Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
kernel/bpf/verifier.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c602007bf583..39f7f633b4d6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12336,6 +12336,14 @@ get_kfunc_arg_type(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
if (is_kfunc_release(meta) && arg == 0)
arg_type |= OBJ_RELEASE;
+ /*
+ * A KF_RCU kfunc accepts an RCU-protected pointer where it would
+ * otherwise demand a referenced or trusted one. Other argument kinds
+ * have their own provenance requirements and must not inherit MEM_RCU.
+ */
+ if (base_type(arg_type) == ARG_PTR_TO_BTF_ID && is_kfunc_rcu(meta))
+ arg_type |= MEM_RCU;
+
return arg_type;
}
@@ -13275,7 +13283,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
reg2btf_ids[base_type(reg->type)]) {
if (!is_trusted_reg(env, reg) ||
bpf_type_has_unsafe_modifiers(reg->type)) {
- if (!is_kfunc_rcu(meta)) {
+ if (!(arg_type & MEM_RCU)) {
const char *expected_type;
expected_type = bpf_diag_fmt_btf_type(env, btf, ref_id);
--
2.52.0
next prev parent reply other threads:[~2026-09-11 22:04 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-11 22:03 [PATCH bpf-next v2 00/23] Unify helper and kfunc argument checks Amery Hung
2026-09-11 22:03 ` [PATCH bpf-next v2 01/23] bpf: Pass call metadata through shared " Amery Hung
2026-09-11 22:03 ` [PATCH bpf-next v2 02/23] bpf: Address check_func_arg() arguments by argno Amery Hung
2026-09-11 22:03 ` [PATCH bpf-next v2 03/23] bpf: Only compare func_id against BPF_FUNC_* for helper calls Amery Hung
2026-09-11 22:03 ` [PATCH bpf-next v2 04/23] bpf: Only compare func_id against kfunc BTF IDs for kfunc calls Amery Hung
2026-09-11 22:03 ` [PATCH bpf-next v2 05/23] bpf: Clarify unused and scalar function argument types Amery Hung
2026-09-11 22:19 ` sashiko-bot
2026-09-11 22:03 ` [PATCH bpf-next v2 06/23] bpf: Unify kfunc argument kinds with enum bpf_arg_type Amery Hung
2026-09-11 22:26 ` sashiko-bot
2026-09-11 22:03 ` [PATCH bpf-next v2 07/23] bpf: Classify kfunc arguments the verifier ignores Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 08/23] bpf: Align helper and kfunc ARG_PTR_TO_PROG_AUX handling Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 09/23] bpf: Set OBJ_RELEASE when generating kfunc argument types Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 10/23] bpf: Set MEM_UNINIT and dynptr subtypes when generating kfunc arg types Amery Hung
2026-09-11 22:04 ` Amery Hung [this message]
2026-09-11 22:04 ` [PATCH bpf-next v2 12/23] bpf: Resolve BTF ID of ARG_PTR_TO_BTF_ID in kfunc bpf_func_proto Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 13/23] bpf: Resolve ARG_PTR_TO_MEM | MEM_FIXED_SIZE size " Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 14/23] bpf: Consolidate runtime argument type resolution Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 15/23] bpf: Consolidate nullable argument validation Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 16/23] bpf: Drop redundant BTF pointer helper write rejection Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 17/23] bpf: Consolidate helper and kfunc PTR_TO_BTF_ID argument matching Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 18/23] bpf: Admit kfunc argument registers through check_reg_type() Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 19/23] bpf: Consolidate function call pkt_access validation Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 20/23] selftests/bpf: Test kfunc packet memory direct writes Amery Hung
2026-09-11 22:36 ` sashiko-bot
2026-09-11 22:04 ` [PATCH bpf-next v2 21/23] bpf: Consolidate release argument validation Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 22/23] selftests/bpf: Test nullable per-CPU kptr identity after exchange Amery Hung
2026-09-11 22:04 ` [PATCH bpf-next v2 23/23] bpf: Check helper and kfunc arguments in one path Amery Hung
2026-09-12 3:20 ` [PATCH bpf-next v2 00/23] Unify helper and kfunc argument checks patchwork-bot+netdevbpf
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