From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: Eduard Zingerman <eddyz87@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Emil Tsalapatis <emil@etsalapatis.com>, Tejun Heo <tj@kernel.org>,
Amery Hung <ameryhung@gmail.com>,
kkd@meta.com, kernel-team@meta.com
Subject: [PATCH bpf-next v4 4/8] selftests/bpf: Cover helper memory access permissions
Date: Fri, 18 Sep 2026 07:28:58 +0200 [thread overview]
Message-ID: <20260918052906.12226-5-memxor@gmail.com> (raw)
In-Reply-To: <20260918052906.12226-1-memxor@gmail.com>
From: Eduard Zingerman <eddyz87@gmail.com>
Check that fixed-size and sized helper in/out buffers require both read
and write permission. Cover bpf_check_mtu() and bpf_fib_lookup(), including
read/write buffers as positive controls.
Keep rejecting read-only buffers for bpf_check_mtu(), and verify that a
write-only map remains a valid destination for bpf_get_current_comm(),
whose output is annotated MEM_UNINIT.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
.../progs/verifier_helper_access_var_len.c | 41 ++++++++++
.../selftests/bpf/progs/verifier_mtu.c | 75 +++++++++++++++++++
2 files changed, 116 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/verifier_helper_access_var_len.c b/tools/testing/selftests/bpf/progs/verifier_helper_access_var_len.c
index d1452ef6f2f9..6d2c6aec129f 100644
--- a/tools/testing/selftests/bpf/progs/verifier_helper_access_var_len.c
+++ b/tools/testing/selftests/bpf/progs/verifier_helper_access_var_len.c
@@ -822,4 +822,45 @@ __naked void bytes_no_leak_init_memory(void)
: __clobber_all);
}
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __uint(map_flags, BPF_F_WRONLY_PROG);
+ __type(key, __u32);
+ __type(value, struct bpf_fib_lookup);
+} map_fib_wo SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __type(key, __u32);
+ __type(value, struct bpf_fib_lookup);
+} map_fib_rw SEC(".maps");
+
+SEC("tc")
+__failure __msg("read from map forbidden")
+int writeonly_sized_input(struct __sk_buff *ctx)
+{
+ struct bpf_fib_lookup *params;
+ __u32 key = 0;
+
+ params = bpf_map_lookup_elem(&map_fib_wo, &key);
+ if (params)
+ bpf_fib_lookup(ctx, params, sizeof(*params), 0);
+ return 0;
+}
+
+SEC("tc")
+__success
+int readwrite_sized_input(struct __sk_buff *ctx)
+{
+ struct bpf_fib_lookup *params;
+ __u32 key = 0;
+
+ params = bpf_map_lookup_elem(&map_fib_rw, &key);
+ if (params)
+ bpf_fib_lookup(ctx, params, sizeof(*params), 0);
+ return 0;
+}
+
char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/verifier_mtu.c b/tools/testing/selftests/bpf/progs/verifier_mtu.c
index 256956ea1ac5..af89ce3d30f7 100644
--- a/tools/testing/selftests/bpf/progs/verifier_mtu.c
+++ b/tools/testing/selftests/bpf/progs/verifier_mtu.c
@@ -17,4 +17,79 @@ int tc_uninit_mtu(struct __sk_buff *ctx)
return TCX_PASS;
}
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __uint(map_flags, BPF_F_WRONLY_PROG);
+ __type(key, __u32);
+ __type(value, __u32);
+} map_mtu_wo SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __type(key, __u32);
+ __type(value, __u32);
+} map_mtu_rw SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __uint(map_flags, BPF_F_RDONLY_PROG);
+ __type(key, __u32);
+ __type(value, __u32);
+} map_mtu_ro SEC(".maps");
+
+SEC("tc/ingress")
+__failure __msg("read from map forbidden")
+int tc_writeonly_mtu(struct __sk_buff *ctx)
+{
+ __u32 key = 0;
+ __u32 *mtu;
+
+ mtu = bpf_map_lookup_elem(&map_mtu_wo, &key);
+ if (mtu)
+ bpf_check_mtu(ctx, 0, mtu, 0, 0);
+ return TCX_PASS;
+}
+
+SEC("tc/ingress")
+__success
+int tc_readwrite_mtu(struct __sk_buff *ctx)
+{
+ __u32 key = 0;
+ __u32 *mtu;
+
+ mtu = bpf_map_lookup_elem(&map_mtu_rw, &key);
+ if (mtu)
+ bpf_check_mtu(ctx, 0, mtu, 0, 0);
+ return TCX_PASS;
+}
+
+SEC("tc/ingress")
+__failure __msg("write into map forbidden")
+int tc_readonly_mtu(struct __sk_buff *ctx)
+{
+ __u32 key = 0;
+ __u32 *mtu;
+
+ mtu = bpf_map_lookup_elem(&map_mtu_ro, &key);
+ if (mtu)
+ bpf_check_mtu(ctx, 0, mtu, 0, 0);
+ return TCX_PASS;
+}
+
+SEC("tc/ingress")
+__success
+int tc_writeonly_output(struct __sk_buff *ctx)
+{
+ __u32 key = 0;
+ __u32 *out;
+
+ out = bpf_map_lookup_elem(&map_mtu_wo, &key);
+ if (out)
+ bpf_get_current_comm(out, sizeof(*out));
+ return TCX_PASS;
+}
+
char LICENSE[] SEC("license") = "GPL";
--
2.53.0
next prev parent reply other threads:[~2026-09-18 5:29 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-18 5:28 [PATCH bpf-next v4 0/8] Fix generic __uninit kfunc output buffers Kumar Kartikeya Dwivedi
2026-09-18 5:28 ` [PATCH bpf-next v4 1/8] selftests/bpf: Allow privileged preparation for capability tests Kumar Kartikeya Dwivedi
2026-09-18 5:28 ` [PATCH bpf-next v4 2/8] bpf: Record raw memory arguments during argument checking Kumar Kartikeya Dwivedi
2026-09-18 6:35 ` bot+bpf-ci
2026-09-18 16:24 ` Eduard Zingerman
2026-09-18 5:28 ` [PATCH bpf-next v4 3/8] bpf: Check read access for initialized writable memory arguments Kumar Kartikeya Dwivedi
2026-09-18 5:50 ` sashiko-bot
2026-09-18 17:46 ` Eduard Zingerman
2026-09-18 18:01 ` Amery Hung
2026-09-18 5:28 ` Kumar Kartikeya Dwivedi [this message]
2026-09-18 6:17 ` [PATCH bpf-next v4 4/8] selftests/bpf: Cover helper memory access permissions bot+bpf-ci
2026-09-18 5:28 ` [PATCH bpf-next v4 5/8] bpf: Fix generic __uninit kfunc output buffers Kumar Kartikeya Dwivedi
2026-09-18 6:35 ` bot+bpf-ci
2026-09-18 17:50 ` Eduard Zingerman
2026-09-18 5:29 ` [PATCH bpf-next v4 6/8] selftests/bpf: Cover generic __uninit output initialization Kumar Kartikeya Dwivedi
2026-09-18 5:29 ` [PATCH bpf-next v4 7/8] bpf: Support multiple __uninit kfunc output arguments Kumar Kartikeya Dwivedi
2026-09-18 5:29 ` [PATCH bpf-next v4 8/8] selftests/bpf: Cover __uninit kfunc output argument slots Kumar Kartikeya Dwivedi
2026-09-18 6:35 ` bot+bpf-ci
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