From nobody Sat Feb 7 06:21:32 2026 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 C9CB9283124; Wed, 29 Oct 2025 12:23:00 +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=1761740580; cv=none; b=SjaKaD/aIdeMzcOUK3RWFWtPB1SbxFx5eXhBI1uengvx8+xlR7ZErcQnfOK6W0vtw+zWM3ZFZwnbxZUuTsV0m7cnk47fOJB7A02x5UEDXvgVsTc4Qx5AoJzrJfsaWcBd9PTZIyH3GMtrRnPNSAtumFflFCbALkfEt61UsFpZZ4s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761740580; c=relaxed/simple; bh=zOSZXXVQ1jVkT7WHK+88OLa6Cp/PXPPixfxVAVT9vUI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=intvNTD/3o0mZiWqEuRol36GnNd1ImiJRcrUUauwEdC6eqbZzcrGjrc76aB0dHgmzT62YJZK4WFO2o9XMVWrx2yJwf0BIPznaz7kiM5n1SUi0/Z6f3xDg7V9myhMV4Fz6f7TGbJKSDWjuWys09F5acDYXvCbVToFpZKWAr5fscU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pF3sY0bU; 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="pF3sY0bU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31C7DC4CEFF; Wed, 29 Oct 2025 12:22:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761740580; bh=zOSZXXVQ1jVkT7WHK+88OLa6Cp/PXPPixfxVAVT9vUI=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=pF3sY0bUKeKQKSFV/M0SbqE1dcZRoZgodV95fy7X6SlAlverqnHXm6yBcWz6J5l+c qeAT6DQkcvHcHQoR58sG+W+CWwlaKlXgunPWbAMVz4sUXd9CP2s0TUHClGeKqu3SkK TfK0Rmtcs0qUHSCqLs4jWfjg94RNlPpI1lsxllBl0XQTx+ZN/Wo4L3nKfDMb1cqYWa kKGG394cJMTycufOgA4Tjus+UKL3lFhDbWKpuJ2AwHk18LCRRDBg0crecPHYD6v+Jg //JPS9lwjqE7dG+bMqZLJSV9XwfMw04hYNCMQBLOMR489NNXzvxyxDPYKRx9HanhWV hu361/j6hntLg== From: Christian Brauner Date: Wed, 29 Oct 2025 13:20:41 +0100 Subject: [PATCH v4 28/72] selftests/namespaces: sixth active reference count tests Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251029-work-namespace-nstree-listns-v4-28-2e6f823ebdc0@kernel.org> References: <20251029-work-namespace-nstree-listns-v4-0-2e6f823ebdc0@kernel.org> In-Reply-To: <20251029-work-namespace-nstree-listns-v4-0-2e6f823ebdc0@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=5791; i=brauner@kernel.org; h=from:subject:message-id; bh=zOSZXXVQ1jVkT7WHK+88OLa6Cp/PXPPixfxVAVT9vUI=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWQysfX+M7oQ9CqwSdg3c477bg91fWabd9bhbDuYd35tl NnwSKqmo5SFQYyLQVZMkcWh3SRcbjlPxWajTA2YOaxMIEMYuDgFYCLJ9xj+B3q0nz/044Z5R/dS 30uze3TMvsUcVuY12hjbviVGN+N4IcP/XLZLwbaGDz4E3eX/qPLqpP6OiatsOnrfzk+M9+YrlD3 ODwA= 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 | 155 +++++++++++++++++= ++++ 1 file changed, 155 insertions(+) diff --git a/tools/testing/selftests/namespaces/ns_active_ref_test.c b/tool= s/testing/selftests/namespaces/ns_active_ref_test.c index f4e92b772f70..50653096fcb6 100644 --- a/tools/testing/selftests/namespaces/ns_active_ref_test.c +++ b/tools/testing/selftests/namespaces/ns_active_ref_test.c @@ -448,4 +448,159 @@ TEST(pidns_active_ref_lifecycle) ASSERT_TRUE(errno =3D=3D ENOENT || errno =3D=3D ESTALE); } =20 +/* + * 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 =3D fork(); + ASSERT_GE(pid, 0); + + if (pid =3D=3D 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 =3D 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 =3D 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 =3D (struct file_handle *)buf; + handle->handle_bytes =3D MAX_HANDLE_SZ; + ret =3D 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=3D%u)", handle->handle_bytes); + + /* Send file handle to parent */ + ret =3D 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 =3D 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 =3D read(pipe_child_ready[0], buf, sizeof(buf)); + close(pipe_child_ready[0]); + ASSERT_GT(ret, 0); + handle =3D (struct file_handle *)buf; + + TH_LOG("Parent: received %d bytes, handle size=3D%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 =3D 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 =3D '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)); + ASSERT_EQ(WEXITSTATUS(status), 0); + + 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 =3D open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY); + ASSERT_GE(fd2, 0); + + 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=3D%lu, fd2=3D%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 - ina= ctive)"); + fd2 =3D open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY); + ASSERT_LT(fd2, 0); + /* Should fail with ENOENT (inactive) or ESTALE (gone) */ + TH_LOG("Reopen failed as expected: %s (errno=3D%d)", strerror(errno), err= no); + ASSERT_TRUE(errno =3D=3D ENOENT || errno =3D=3D ESTALE); +} + TEST_HARNESS_MAIN --=20 2.47.3