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Tue, 09 Jun 2026 01:37:12 -0700 (PDT) Received: from x1.tail0e71db.ts.net ([46.140.7.198]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-490c2d5d2b4sm304149135e9.2.2026.06.09.01.37.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Jun 2026 01:37:12 -0700 (PDT) From: Ruslan Valiyev To: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, martin.lau@linux.dev, memxor@gmail.com Cc: song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, mykyta.yatsenko5@gmail.com Subject: [PATCH v3 bpf-next] selftests/bpf: add tests for arena vma split and fork Date: Tue, 9 Jun 2026 10:37:09 +0200 Message-ID: <20260609083709.168755-1-linuxoid@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add a test that an arena map's mmap()ed region cannot be split by a partial munmap() (the "split" subtest, which expects -EINVAL) and is not inherited across fork() (the "fork" subtest, where mincore() reports the child's range as unmapped). Signed-off-by: Ruslan Valiyev --- v3: - Consolidate into one file with a shared setup helper and two subtests. - Put the opening /* of the multi-line comment on its own line. v2: - Drop the regression-test framing and per-callback details. - Split the original single test; unpack the mincore() check. .../selftests/bpf/prog_tests/arena_vma.c | 94 +++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/arena_vma.c diff --git a/tools/testing/selftests/bpf/prog_tests/arena_vma.c b/tools/testing/selftests/bpf/prog_tests/arena_vma.c new file mode 100644 index 0000000000000..f6c07cd31d08b --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/arena_vma.c @@ -0,0 +1,94 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include + +/* Make sure arena mappings cannot be split or inherited. */ + +#define NR_PAGES 3 + +static int arena_mmap(int *fd, void **area, size_t *sz) +{ + LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE); + + *sz = (size_t)NR_PAGES * sysconf(_SC_PAGESIZE); + + *fd = bpf_map_create(BPF_MAP_TYPE_ARENA, "arena_vma", 0, 0, NR_PAGES, &opts); + if (!ASSERT_OK_FD(*fd, "arena map create")) + return -1; + + *area = mmap(NULL, *sz, PROT_READ | PROT_WRITE, MAP_SHARED, *fd, 0); + if (!ASSERT_NEQ(*area, MAP_FAILED, "mmap arena")) { + close(*fd); + return -1; + } + return 0; +} + +/* A partial munmap that would split the arena mapping must be rejected. */ +static void split_test(void) +{ + long ps = sysconf(_SC_PAGESIZE); + void *area; + size_t sz; + int fd, ret, err; + + if (arena_mmap(&fd, &area, &sz)) + return; + + ret = munmap((char *)area + ps, ps); + err = errno; + if (ASSERT_ERR(ret, "split munmap")) + ASSERT_EQ(err, EINVAL, "split munmap errno"); + + munmap(area, sz); + close(fd); +} + +/* A forked child must not inherit the arena mapping. */ +static void fork_test(void) +{ + long ps = sysconf(_SC_PAGESIZE); + void *area; + size_t sz; + int fd, ret, status; + pid_t pid; + + if (arena_mmap(&fd, &area, &sz)) + return; + + pid = fork(); + if (pid == 0) { + unsigned char vec; + int rc; + + /* + * If the mapping was not inherited the range is unmapped in + * the child, so mincore() fails with ENOMEM. A success means + * the child wrongly inherited the mapping. + */ + rc = mincore(area, ps, &vec); + if (rc == 0) + _exit(1); + _exit(errno == ENOMEM ? 0 : 2); + } + if (ASSERT_GE(pid, 0, "fork")) { + while ((ret = waitpid(pid, &status, 0)) < 0 && errno == EINTR) + ; + if (ASSERT_EQ(ret, pid, "waitpid")) + ASSERT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0, + "child must not inherit arena mapping"); + } + + munmap(area, sz); + close(fd); +} + +void test_arena_vma(void) +{ + if (test__start_subtest("split")) + split_test(); + if (test__start_subtest("fork")) + fork_test(); +} base-commit: 174914ea551314c52a61713b9c4bde9e42d48073 -- 2.43.0