From: Adethya Srinivasan <adethyasrinivasan@outlook.com>
To: bpf@vger.kernel.org
Cc: Adethya Srinivasan <adethyasrinivasan@outlook.com>,
yonghong.song@linux.dev, ast@kernel.org, daniel@iogearbox.net,
andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com,
martin.lau@linux.dev, song@kernel.org, jolsa@kernel.org,
emil@etsalapatis.com, ihor.solodrai@linux.dev, shuah@kernel.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: [PATCH bpf v2 2/2] selftests/bpf: Check writable iterator attach to a read-only array
Date: Thu, 12 Nov 2026 15:54:07 +0000 [thread overview]
Message-ID: <LO2P302MB019736CF58FAA4C98C6F78AABC702@LO2P302MB0197.GBRP302.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <LO2P302MB0197C0434BCC2A9031E99A18BC702@LO2P302MB0197.GBRP302.PROD.OUTLOOK.COM>
Reuse dump_bpf_array_map(), which writes to ctx->value, and attempt
to attach it to an array with BPF_F_RDONLY_PROG set. Assert that the
attach returns -EACCES and destroy the link if it unexpectedly succeeds.
The test fails on an unfixed kernel and passes with the fix applied.
Signed-off-by: Adethya Srinivasan <adethyasrinivasan@outlook.com>
---
.../selftests/bpf/prog_tests/bpf_iter.c | 35 +++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index c69080ca1..5249b07cd 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -1100,6 +1100,39 @@ static void test_bpf_array_map(void)
bpf_iter_bpf_array_map__destroy(skel);
}
+static void test_bpf_array_map_rdonly(void)
+{
+ DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+ struct bpf_iter_bpf_array_map *skel;
+ union bpf_iter_link_info linfo = {};
+ struct bpf_link *link;
+ int err;
+
+ skel = bpf_iter_bpf_array_map__open();
+ if (!ASSERT_OK_PTR(skel, "bpf_iter_bpf_array_map__open"))
+ return;
+
+ err = bpf_map__set_map_flags(skel->maps.arraymap1, BPF_F_RDONLY_PROG);
+ if (!ASSERT_OK(err, "set_map_flags"))
+ goto out;
+
+ err = bpf_iter_bpf_array_map__load(skel);
+ if (!ASSERT_OK(err, "bpf_iter_bpf_array_map__load"))
+ goto out;
+
+ linfo.map.map_fd = bpf_map__fd(skel->maps.arraymap1);
+ opts.link_info = &linfo;
+ opts.link_info_len = sizeof(linfo);
+ link = bpf_program__attach_iter(skel->progs.dump_bpf_array_map, &opts);
+ err = libbpf_get_error(link);
+ ASSERT_EQ(err, -EACCES, "attach_rdonly_write_iter");
+ if (!err)
+ bpf_link__destroy(link);
+
+out:
+ bpf_iter_bpf_array_map__destroy(skel);
+}
+
static void test_bpf_array_map_iter_fd(void)
{
struct bpf_iter_bpf_array_map *skel;
@@ -1770,6 +1803,8 @@ void test_bpf_iter(void)
test_bpf_percpu_hash_map();
if (test__start_subtest("bpf_array_map"))
test_bpf_array_map();
+ if (test__start_subtest("bpf_array_map_rdonly"))
+ test_bpf_array_map_rdonly();
if (test__start_subtest("bpf_array_map_iter_fd"))
test_bpf_array_map_iter_fd();
if (test__start_subtest("bpf_percpu_array_map"))
prev parent reply other threads:[~2026-11-12 15:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-12 15:54 [PATCH bpf v2 0/2] Reject writable map iterators on read-only maps Adethya Srinivasan
2026-11-12 15:54 ` [PATCH bpf v2 1/2] bpf: " Adethya Srinivasan
2026-11-12 15:54 ` Adethya Srinivasan [this message]
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