From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D0169342149; Tue, 21 Oct 2025 11:45:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761047158; cv=none; b=evz+BpbcM3mZ7orFsZBigajAJLkUFQ0WYxFVRNfJVg8DE2XPpwW0ITqiah2SaB+cjHk3dRNiyUBR6aP+PaNOdyMYdJWr+rnQ7mOZ6huFS4cBGLfBVvtBILF+bmXv9mI0e4T1STvlUFgKrw7YKRvmSwwUNnd+1x/L2JKutZI4oT8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761047158; c=relaxed/simple; bh=uOH3CT+OUgM5Z/Sy7CrxJmBWupBsQ4/yDAh+nMm1LYg=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=TlQiXPnzMXbPjz3wHfofHlkQ5SNOZ5gSCfiaIOjEA59lHKyrgkZhuTqLFIF5rN1iLGtzd32PGPLdRvsUtDSMb2u9o9P5hAFsYuVJZur8stp3bxLgxQyh6uKo/MAVMv63FW7ZMaebVzPV1FmAnEvE44oWKyrOVFqMxfFi5mQhbFY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=H1fi4Gr1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="H1fi4Gr1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7DBC7C4CEF5; Tue, 21 Oct 2025 11:45:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761047158; bh=uOH3CT+OUgM5Z/Sy7CrxJmBWupBsQ4/yDAh+nMm1LYg=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=H1fi4Gr1EFMYDUL1pzIJeZIZDzQ/JHPbq1JUifXDaByHwA1mJ8p5FmttWqDmceJbP dONWJKpu8Gy/+14E5zseA9FBiERE7lY65IrvdMxIO1gCrogPd+0kNRDcH+BFdPzZ1D nTq2qCUgfGIeeSVM1Ppqq5jL3lITA9gibMnOdqOhgHHc08iBFtMlrJmwvZqiA4vdtt BQYfngfQYSAUyey6+PW4mnlumXPniQIbuDlYUX151DA15/rw0orrcwMmokxH9B5u3E /UJuOoFRKvdEb6R5AUJk9zi0U7KcD+lTwJhwDY+WXvPJUghcwx/jAjnQBOj2fH2eoL ze6HPLUp1lGMA== From: Christian Brauner Date: Tue, 21 Oct 2025 13:43:30 +0200 Subject: [PATCH RFC DRAFT 24/50] selftests/namespaces: sixth active reference count tests Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251021-work-namespace-nstree-listns-v1-24-ad44261a8a5b@kernel.org> References: <20251021-work-namespace-nstree-listns-v1-0-ad44261a8a5b@kernel.org> In-Reply-To: <20251021-work-namespace-nstree-listns-v1-0-ad44261a8a5b@kernel.org> To: linux-fsdevel@vger.kernel.org, Josef Bacik , Jeff Layton Cc: Jann Horn , Mike Yuan , =?utf-8?q?Zbigniew_J=C4=99drzejewski-Szmek?= , Lennart Poettering , Daan De Meyer , Aleksa Sarai , Amir Goldstein , Tejun Heo , Johannes Weiner , Thomas Gleixner , Alexander Viro , Jan Kara , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, bpf@vger.kernel.org, Eric Dumazet , Jakub Kicinski , netdev@vger.kernel.org, Arnd Bergmann , Christian Brauner X-Mailer: b4 0.15-dev-96507 X-Developer-Signature: v=1; a=openpgp-sha256; l=6091; i=brauner@kernel.org; h=from:subject:message-id; bh=uOH3CT+OUgM5Z/Sy7CrxJmBWupBsQ4/yDAh+nMm1LYg=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWR8L3y7e5/o7xv/EhY+i315crLvttDN6j4dkTOcn02Sd Gxo5ObW6ShlYRDjYpAVU2RxaDcJl1vOU7HZKFMDZg4rE8gQBi5OAZiIjjYjw/ujKpImcTJM85P4 t5TaLZnWN3mf5Od1Agr/pEy0vnnsK2b4ZxOtK8pknJ2QYnqMeTr/v9NcjPMzv5vfeThp9ef+3B2 BTAA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Test that an open file descriptor keeps a namespace active. Even after the creating process exits, the namespace should remain active as long as an fd is held open. Signed-off-by: Christian Brauner --- .../selftests/namespaces/ns_active_ref_test.c | 168 +++++++++++++++++++++ 1 file changed, 168 insertions(+) diff --git a/tools/testing/selftests/namespaces/ns_active_ref_test.c b/tools/testing/selftests/namespaces/ns_active_ref_test.c index 66665bd39e9b..dbb1eb8a04b2 100644 --- a/tools/testing/selftests/namespaces/ns_active_ref_test.c +++ b/tools/testing/selftests/namespaces/ns_active_ref_test.c @@ -473,4 +473,172 @@ TEST(pidns_active_ref_lifecycle) } } +/* + * Test that an open file descriptor keeps a namespace active. + * Even after the creating process exits, the namespace should remain + * active as long as an fd is held open. + */ +TEST(ns_fd_keeps_active) +{ + struct file_handle *handle; + int mount_id; + int ret; + int nsfd; + int pipe_child_ready[2]; + int pipe_parent_ready[2]; + pid_t pid; + int status; + char buf[sizeof(*handle) + MAX_HANDLE_SZ]; + char sync_byte; + char proc_path[64]; + + ASSERT_EQ(pipe(pipe_child_ready), 0); + ASSERT_EQ(pipe(pipe_parent_ready), 0); + + pid = fork(); + ASSERT_GE(pid, 0); + + if (pid == 0) { + /* Child process */ + close(pipe_child_ready[0]); + close(pipe_parent_ready[1]); + + TH_LOG("Child: creating new network namespace"); + + /* Create new network namespace */ + ret = unshare(CLONE_NEWNET); + if (ret < 0) { + TH_LOG("Child: unshare(CLONE_NEWNET) failed: %s", strerror(errno)); + close(pipe_child_ready[1]); + close(pipe_parent_ready[0]); + exit(1); + } + + TH_LOG("Child: network namespace created successfully"); + + /* Get file handle for the namespace */ + nsfd = open("/proc/self/ns/net", O_RDONLY); + if (nsfd < 0) { + TH_LOG("Child: failed to open /proc/self/ns/net: %s", strerror(errno)); + close(pipe_child_ready[1]); + close(pipe_parent_ready[0]); + exit(1); + } + + TH_LOG("Child: opened namespace fd %d", nsfd); + + handle = (struct file_handle *)buf; + handle->handle_bytes = MAX_HANDLE_SZ; + ret = name_to_handle_at(nsfd, "", handle, &mount_id, AT_EMPTY_PATH); + close(nsfd); + + if (ret < 0) { + TH_LOG("Child: name_to_handle_at failed: %s", strerror(errno)); + close(pipe_child_ready[1]); + close(pipe_parent_ready[0]); + exit(1); + } + + TH_LOG("Child: got file handle (bytes=%u)", handle->handle_bytes); + + /* Send file handle to parent */ + ret = write(pipe_child_ready[1], buf, sizeof(*handle) + handle->handle_bytes); + TH_LOG("Child: sent %d bytes of file handle to parent", ret); + close(pipe_child_ready[1]); + + /* Wait for parent to open the fd */ + TH_LOG("Child: waiting for parent to open fd"); + ret = read(pipe_parent_ready[0], &sync_byte, 1); + close(pipe_parent_ready[0]); + + TH_LOG("Child: parent signaled (read %d bytes), exiting now", ret); + /* Exit - namespace should stay active because parent holds fd */ + exit(0); + } + + /* Parent process */ + close(pipe_child_ready[1]); + close(pipe_parent_ready[0]); + + TH_LOG("Parent: reading file handle from child"); + + /* Read file handle from child */ + ret = read(pipe_child_ready[0], buf, sizeof(buf)); + close(pipe_child_ready[0]); + ASSERT_GT(ret, 0); + handle = (struct file_handle *)buf; + + TH_LOG("Parent: received %d bytes, handle size=%u", ret, handle->handle_bytes); + + /* Open the child's namespace while it's still alive */ + snprintf(proc_path, sizeof(proc_path), "/proc/%d/ns/net", pid); + TH_LOG("Parent: opening child's namespace at %s", proc_path); + nsfd = open(proc_path, O_RDONLY); + if (nsfd < 0) { + TH_LOG("Parent: failed to open %s: %s", proc_path, strerror(errno)); + close(pipe_parent_ready[1]); + kill(pid, SIGKILL); + waitpid(pid, NULL, 0); + SKIP(return, "Failed to open child's namespace"); + } + + TH_LOG("Parent: opened child's namespace, got fd %d", nsfd); + + /* Signal child that we have the fd */ + sync_byte = 'G'; + write(pipe_parent_ready[1], &sync_byte, 1); + close(pipe_parent_ready[1]); + TH_LOG("Parent: signaled child that we have the fd"); + + /* Wait for child to exit */ + waitpid(pid, &status, 0); + ASSERT_TRUE(WIFEXITED(status)); + + if (WEXITSTATUS(status) != 0) { + close(nsfd); + SKIP(return, "Child failed to create namespace"); + } + + TH_LOG("Child exited, parent holds fd %d to namespace", nsfd); + + /* + * Namespace should still be ACTIVE because we hold an fd. + * We should be able to reopen it via file handle. + */ + TH_LOG("Attempting to reopen namespace via file handle (should succeed - fd held)"); + int fd2 = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY); + if (fd2 < 0) { + close(nsfd); + TH_LOG("ERROR: Failed to reopen active namespace (fd held): %s (errno=%d)", + strerror(errno), errno); + ASSERT_TRUE(false); + } + + TH_LOG("Successfully reopened namespace via file handle, got fd %d", fd2); + + /* Verify it's the same namespace */ + struct stat st1, st2; + ASSERT_EQ(fstat(nsfd, &st1), 0); + ASSERT_EQ(fstat(fd2, &st2), 0); + TH_LOG("Namespace inodes: nsfd=%lu, fd2=%lu", st1.st_ino, st2.st_ino); + ASSERT_EQ(st1.st_ino, st2.st_ino); + close(fd2); + + /* Now close the fd - namespace should become inactive */ + TH_LOG("Closing fd %d - namespace should become inactive", nsfd); + close(nsfd); + + /* Now reopening should fail - namespace is inactive */ + TH_LOG("Attempting to reopen namespace via file handle (should fail - inactive)"); + fd2 = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY); + if (fd2 >= 0) { + close(fd2); + TH_LOG("ERROR: Namespace still active after closing all fds (fd=%d)", fd2); + } else { + /* Should fail with ENOENT (inactive) or ESTALE (gone) */ + TH_LOG("Reopen failed as expected: %s (errno=%d)", strerror(errno), errno); + ASSERT_TRUE(errno == ENOENT || errno == ESTALE); + } +} + TEST_HARNESS_MAIN -- 2.47.3