From nobody Sun Feb 8 17:42:39 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 7194B380F36; Wed, 22 Oct 2025 16:10:37 +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=1761149437; cv=none; b=mvnXtvTXQmZKYCl/G87EhouSZO/Am9RsDp8/21vPbymRxzIzk4inBjXSPQy+A/wYi9loa5oYpRDm+t6BKpBTxj3V7H502XRz7wkvaxA+InG6SqYNGw27N54a50Ukv5qTHbxgvBWBruzr1yiChjFL2ClUGIK8vmvxeCnVdihX7Sc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761149437; c=relaxed/simple; bh=Jz2qZpRe8+RR2mHCIjuTDi9/gaS5B8ErVeSfakXzmUk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=N7F8meEGyiSzRi2b5PztyhinLHEvUdwqMzW06BUzZaub1IY0qyIdtvbV4MoWsC26WMhua39YUMd+Mpu0trQvTGngqkACK2gNT8lz8+cUGR9lXCmiDPZKldKVoS8gl+akgrGYadiWHa88Z1zcGbgM4IbAn0FWS1e18bfQQCZY7NY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CKNeh0Es; 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="CKNeh0Es" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61B97C4CEFD; Wed, 22 Oct 2025 16:10:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761149437; bh=Jz2qZpRe8+RR2mHCIjuTDi9/gaS5B8ErVeSfakXzmUk=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=CKNeh0Esf68YkqbfBA7BnsGES8vnsy3bC4GL/TbxCX+CjBSohB+fqiaCzc2U/gdk/ CNBMsnejsaFHJUZeNyT39s4ZJdJAa9UhH2tZdggwBTQJP2ConKKY2dX3R6GfUTFeFx jVLhpSXEGuAsRGgTn8b9vESouduRugivaVMo7C6u9cL4bKO2/pnaD3gi0J3VgdF5GA TWpeNoovW4Zvx3EgvqgkulEimoKLfeoVKM7fHIjXJfHcu65NAQJE6PGJaIyuUxjhO6 um+TlRDuP/NdByRfrQToM7G4p+wfiDit3CFveMhP4YcNbg49jzJmSJcDAmafcofdqs 7ZpOqzdW9223A== From: Christian Brauner Date: Wed, 22 Oct 2025 18:06:29 +0200 Subject: [PATCH v2 51/63] selftests/namespaces: seventh listns() permission test 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: <20251022-work-namespace-nstree-listns-v2-51-71a588572371@kernel.org> References: <20251022-work-namespace-nstree-listns-v2-0-71a588572371@kernel.org> In-Reply-To: <20251022-work-namespace-nstree-listns-v2-0-71a588572371@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=3549; i=brauner@kernel.org; h=from:subject:message-id; bh=Jz2qZpRe8+RR2mHCIjuTDi9/gaS5B8ErVeSfakXzmUk=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWT8ZHjO9p3XTJtl0rI3+hoLpm1kaLJ9pHl4o953ycu1/ aY3ZRnedpSyMIhxMciKKbI4tJuEyy3nqdhslKkBM4eVCWQIAxenAEzE3o7hf4LhhvbAZHvj4w58 1xJrOOWe5S+TlVr6697LIgd1gayzzAz/HU5IKvj7ehZfWG6YqMruYqFkye5rOn3BK5YEiU2sUnO ZAQ== X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Test that dropping CAP_SYS_ADMIN restricts what we can see. Signed-off-by: Christian Brauner --- .../selftests/namespaces/listns_permissions_test.c | 111 +++++++++++++++++= ++++ 1 file changed, 111 insertions(+) diff --git a/tools/testing/selftests/namespaces/listns_permissions_test.c b= /tools/testing/selftests/namespaces/listns_permissions_test.c index 709250ce1542..9d1767e8b804 100644 --- a/tools/testing/selftests/namespaces/listns_permissions_test.c +++ b/tools/testing/selftests/namespaces/listns_permissions_test.c @@ -663,4 +663,115 @@ TEST(listns_cap_sys_admin_inside_userns) TH_LOG("Process can see user namespace it has CAP_SYS_ADMIN inside of"); } =20 +/* + * Test that dropping CAP_SYS_ADMIN restricts what we can see. + */ +TEST(listns_drop_cap_sys_admin) +{ + cap_t caps; + cap_value_t cap_list[1] =3D { CAP_SYS_ADMIN }; + + /* This test needs to start with CAP_SYS_ADMIN */ + caps =3D cap_get_proc(); + if (!caps) { + SKIP(return, "Cannot get capabilities"); + } + + cap_flag_value_t cap_val; + if (cap_get_flag(caps, CAP_SYS_ADMIN, CAP_EFFECTIVE, &cap_val) < 0) { + cap_free(caps); + SKIP(return, "Cannot check CAP_SYS_ADMIN"); + } + + if (cap_val !=3D CAP_SET) { + cap_free(caps); + SKIP(return, "Test needs CAP_SYS_ADMIN to start"); + } + cap_free(caps); + + int pipefd[2]; + pid_t pid; + int status; + bool correct; + ssize_t count_before, count_after; + + ASSERT_EQ(pipe(pipefd), 0); + + pid =3D fork(); + ASSERT_GE(pid, 0); + + if (pid =3D=3D 0) { + struct ns_id_req req =3D { + .size =3D sizeof(req), + .spare =3D 0, + .ns_id =3D 0, + .ns_type =3D CLONE_NEWNET, + .spare2 =3D 0, + .user_ns_id =3D LISTNS_CURRENT_USER, + }; + __u64 ns_ids_before[100]; + ssize_t count_before; + __u64 ns_ids_after[100]; + ssize_t count_after; + bool correct; + + close(pipefd[0]); + + /* Create user namespace */ + if (setup_userns() < 0) { + close(pipefd[1]); + exit(1); + } + + /* Count namespaces with CAP_SYS_ADMIN */ + count_before =3D sys_listns(&req, ns_ids_before, ARRAY_SIZE(ns_ids_befor= e), 0); + + /* Drop CAP_SYS_ADMIN */ + caps =3D cap_get_proc(); + if (caps) { + cap_set_flag(caps, CAP_EFFECTIVE, 1, cap_list, CAP_CLEAR); + cap_set_flag(caps, CAP_PERMITTED, 1, cap_list, CAP_CLEAR); + cap_set_proc(caps); + cap_free(caps); + } + + /* Ensure we can't regain the capability */ + prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); + + /* Count namespaces without CAP_SYS_ADMIN */ + count_after =3D sys_listns(&req, ns_ids_after, ARRAY_SIZE(ns_ids_after),= 0); + + /* Without CAP_SYS_ADMIN, we should see same or fewer namespaces */ + correct =3D (count_after <=3D count_before); + + write(pipefd[1], &correct, sizeof(correct)); + write(pipefd[1], &count_before, sizeof(count_before)); + write(pipefd[1], &count_after, sizeof(count_after)); + close(pipefd[1]); + exit(0); + } + + /* Parent */ + close(pipefd[1]); + + correct =3D false; + count_before =3D 0; + count_after =3D 0; + read(pipefd[0], &correct, sizeof(correct)); + read(pipefd[0], &count_before, sizeof(count_before)); + read(pipefd[0], &count_after, sizeof(count_after)); + close(pipefd[0]); + + waitpid(pid, &status, 0); + ASSERT_TRUE(WIFEXITED(status)); + + if (WEXITSTATUS(status) !=3D 0) { + SKIP(return, "Child failed to setup namespace"); + } + + ASSERT_TRUE(correct); + TH_LOG("With CAP_SYS_ADMIN: %zd namespaces, without: %zd namespaces", + count_before, count_after); +} + TEST_HARNESS_MAIN --=20 2.47.3