netdev - [PATCH bpf-next 2/4] bpf: add destructive kfunc set

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Message-Id: <20220720114652.3020467-3-asavkov@redhat.com>
Date:   Wed, 20 Jul 2022 13:46:50 +0200
From:   Artem Savkov <asavkov@...hat.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        Daniel Vacek <dvacek@...hat.com>,
        Jiri Olsa <olsajiri@...il.com>, Song Liu <song@...nel.org>,
        Artem Savkov <asavkov@...hat.com>
Subject: [PATCH bpf-next 2/4] bpf: add destructive kfunc set

Add BTF_KFUNC_TYPE_DESTRUCTIVE and a new destructive_set in struct
btf_kfunc_id_set. Functions in this set will require CAP_SYS_BOOT
capabilities and BPF_F_DESTRUCTIVE flag.

Signed-off-by: Artem Savkov <asavkov@...hat.com>
---
 include/linux/btf.h   |  2 ++
 kernel/bpf/verifier.c | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 1bfed7fa04287..6c58aa70e8125 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -18,6 +18,7 @@ enum btf_kfunc_type {
 	BTF_KFUNC_TYPE_RELEASE,
 	BTF_KFUNC_TYPE_RET_NULL,
 	BTF_KFUNC_TYPE_KPTR_ACQUIRE,
+	BTF_KFUNC_TYPE_DESTRUCTIVE,
 	BTF_KFUNC_TYPE_MAX,
 };
 
@@ -37,6 +38,7 @@ struct btf_kfunc_id_set {
 			struct btf_id_set *release_set;
 			struct btf_id_set *ret_null_set;
 			struct btf_id_set *kptr_acquire_set;
+			struct btf_id_set *destructive_set;
 		};
 		struct btf_id_set *sets[BTF_KFUNC_TYPE_MAX];
 	};
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c59c3df0fea61..064035e70deac 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7582,6 +7582,18 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		return -EACCES;
 	}
 
+	if (btf_kfunc_id_set_contains(desc_btf, resolve_prog_type(env->prog),
+				      BTF_KFUNC_TYPE_DESTRUCTIVE, func_id)) {
+		if (!env->prog->aux->destructive) {
+			verbose(env, "destructive kfunc calls require BPF_F_DESTRUCTIVE flag\n");
+			return -EACCES;
+		}
+		if (!capable(CAP_SYS_BOOT)) {
+			verbose(env, "destructive kfunc calls require CAP_SYS_BOOT capabilities\n");
+			return -EACCES;
+		}
+	}
+
 	acq = btf_kfunc_id_set_contains(desc_btf, resolve_prog_type(env->prog),
 					BTF_KFUNC_TYPE_ACQUIRE, func_id);
 
-- 
2.35.3