selftests/bpf: Test ringbuf mmap read-only and read-write restrictions

Extend ringbuf selftest to validate read/write and read-only restrictions on
memory mapping consumer/producer/data pages. Ensure no "escalations" from
PROT_READ to PROT_WRITE/PROT_EXEC is allowed. And test that mremap() fails to
expand mmap()'ed area.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210514180726.843157-1-andrii@kernel.org

diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
index de78617..f9a8ae3 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
@@ -86,8 +86,9 @@ void test_ringbuf(void)
        const size_t rec_sz = BPF_RINGBUF_HDR_SZ + sizeof(struct sample);
        pthread_t thread;
        long bg_ret = -1;
-       int err, cnt;
+       int err, cnt, rb_fd;
        int page_size = getpagesize();
+       void *mmap_ptr, *tmp_ptr;
 
        skel = test_ringbuf__open();
        if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
@@ -101,6 +102,52 @@ void test_ringbuf(void)
        if (CHECK(err != 0, "skel_load", "skeleton load failed\n"))
                goto cleanup;
 
+       rb_fd = bpf_map__fd(skel->maps.ringbuf);
+       /* good read/write cons_pos */
+       mmap_ptr = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, rb_fd, 0);
+       ASSERT_OK_PTR(mmap_ptr, "rw_cons_pos");
+       tmp_ptr = mremap(mmap_ptr, page_size, 2 * page_size, MREMAP_MAYMOVE);
+       if (!ASSERT_ERR_PTR(tmp_ptr, "rw_extend"))
+               goto cleanup;
+       ASSERT_ERR(mprotect(mmap_ptr, page_size, PROT_EXEC), "exec_cons_pos_protect");
+       ASSERT_OK(munmap(mmap_ptr, page_size), "unmap_rw");
+
+       /* bad writeable prod_pos */
+       mmap_ptr = mmap(NULL, page_size, PROT_WRITE, MAP_SHARED, rb_fd, page_size);
+       err = -errno;
+       ASSERT_ERR_PTR(mmap_ptr, "wr_prod_pos");
+       ASSERT_EQ(err, -EPERM, "wr_prod_pos_err");
+
+       /* bad writeable data pages */
+       mmap_ptr = mmap(NULL, page_size, PROT_WRITE, MAP_SHARED, rb_fd, 2 * page_size);
+       err = -errno;
+       ASSERT_ERR_PTR(mmap_ptr, "wr_data_page_one");
+       ASSERT_EQ(err, -EPERM, "wr_data_page_one_err");
+       mmap_ptr = mmap(NULL, page_size, PROT_WRITE, MAP_SHARED, rb_fd, 3 * page_size);
+       ASSERT_ERR_PTR(mmap_ptr, "wr_data_page_two");
+       mmap_ptr = mmap(NULL, 2 * page_size, PROT_WRITE, MAP_SHARED, rb_fd, 2 * page_size);
+       ASSERT_ERR_PTR(mmap_ptr, "wr_data_page_all");
+
+       /* good read-only pages */
+       mmap_ptr = mmap(NULL, 4 * page_size, PROT_READ, MAP_SHARED, rb_fd, 0);
+       if (!ASSERT_OK_PTR(mmap_ptr, "ro_prod_pos"))
+               goto cleanup;
+
+       ASSERT_ERR(mprotect(mmap_ptr, 4 * page_size, PROT_WRITE), "write_protect");
+       ASSERT_ERR(mprotect(mmap_ptr, 4 * page_size, PROT_EXEC), "exec_protect");
+       ASSERT_ERR_PTR(mremap(mmap_ptr, 0, 4 * page_size, MREMAP_MAYMOVE), "ro_remap");
+       ASSERT_OK(munmap(mmap_ptr, 4 * page_size), "unmap_ro");
+
+       /* good read-only pages with initial offset */
+       mmap_ptr = mmap(NULL, page_size, PROT_READ, MAP_SHARED, rb_fd, page_size);
+       if (!ASSERT_OK_PTR(mmap_ptr, "ro_prod_pos"))
+               goto cleanup;
+
+       ASSERT_ERR(mprotect(mmap_ptr, page_size, PROT_WRITE), "write_protect");
+       ASSERT_ERR(mprotect(mmap_ptr, page_size, PROT_EXEC), "exec_protect");
+       ASSERT_ERR_PTR(mremap(mmap_ptr, 0, 3 * page_size, MREMAP_MAYMOVE), "ro_remap");
+       ASSERT_OK(munmap(mmap_ptr, page_size), "unmap_ro");
+
        /* only trigger BPF program for current process */
        skel->bss->pid = getpid();