From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from picard.linux.it (picard.linux.it [213.254.12.146]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DAB4A606A31A for ; Wed, 28 Oct 2026 06:48:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=lists.linux.it header.i=@lists.linux.it header.a=rsa-sha256 header.s=picard header.b=XkOUfgZL; dkim=fail reason="signature verification failed" (2048-bit key, unprotected) header.d=tuta.io header.i=@tuta.io header.a=rsa-sha256 header.s=s1 header.b=BxZY/fNp DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=lists.linux.it; i=@lists.linux.it; q=dns/txt; s=picard; t=1793170109; h=date : to : message-id : mime-version : subject : list-id : list-unsubscribe : list-archive : list-post : list-help : list-subscribe : from : reply-to : cc : content-type : content-transfer-encoding : sender : from; bh=qlDbBY7bd3ZseERoB7pQz1eHUUyHfUifc43EZ4mEH3g=; b=XkOUfgZLCBqUu7SKqTLoWrJv1VQESJeUbgZZTeh53OHyxLMWOTdqgBGa08Ng3sCAJPthD 03pJ/YLXJvAgqkSqbwslJ4pauPCkGEl1ZFCCFNYso5LoilNsSCy+ZVmp74tqutYbem+hSCi Nl40qVzmemNtgaYszRl01K+j4iKICvQ= Received: from picard.linux.it (localhost [IPv6:::1]) by picard.linux.it (Postfix) with ESMTP id D2D123E1F84 for ; Wed, 28 Oct 2026 07:48:29 +0100 (CET) Received: from in-4.smtp.seeweb.it (in-4.smtp.seeweb.it [IPv6:2001:4b78:1:20::4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (secp384r1)) (No client certificate requested) by picard.linux.it (Postfix) with ESMTPS id 846C33E1DAD for ; Wed, 28 Oct 2026 07:48:05 +0100 (CET) Received: from mail.w14.tutanota.de (mail.w14.tutanota.de [185.205.69.214]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by in-4.smtp.seeweb.it (Postfix) with ESMTPS id 155D81000987 for ; Wed, 28 Oct 2026 07:48:04 +0100 (CET) Received: from tutadb.w10.tutanota.de (w10.api.tuta.com [IPv6:fd:ac::d:10]) by mail.w14.tutanota.de (Postfix) with ESMTP id 4EC3D19DBF5A4 for ; Wed, 28 Oct 2026 07:48:04 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1793170084; s=s1; d=tuta.io; h=From:From:To:To:Subject:Subject:Content-Description:Content-ID:Content-Type:Content-Type:Content-Transfer-Encoding:Content-Transfer-Encoding:Cc:Cc:Date:Date:In-Reply-To:MIME-Version:MIME-Version:Message-ID:Message-ID:Reply-To:References:Sender; bh=2+4ze8mIasfdTPWodEw/lV0/GBUarYltixP89fO82QU=; b=BxZY/fNpMP4CepaOrMfoPXQs+5Zk2rbCos1z6Oi/G3KilJRfDw3Ro40obpvFSI3g XWs7w6NGMATjfZxZy0YmNTa7dxgrFVzXH6lQ8HxxTgpLgJrfQRFx3+jsk6vo5mxKD8C e5PQvYICr74yiwcDKtxnD71BT/jE3/dxwaP7+LG+HGW5PzqrPir5EIt5xXWvRKKYNI2 iObaVWUrbRTtpPujigkeu7HP3knWgggrmorpbF3IuvGWOQpoo98JaTEaowNQh2T/Fg7 zpz/tABLklRzwRLdtqKBJwhWsH9ZqAm56LBFWaumdL/kVUrtz8wW2qZBo2i58YKp3OJ +EHJzRAciw== Date: Wed, 28 Oct 2026 07:48:04 +0100 (CET) To: "ltp@lists.linux.it" Message-ID: X-Archived-By: MIME-Version: 1.0 Feedback-ID: 0127f977f5e13e8051b46c6e7f57d0f95a0470d24b79d7c31d07fdf611cc427ab823e0f4692a810119c92d8768973a9281:TurnOnPrivacy!:tutamail X-Spam-Status: No, score=-16.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Virus-Scanned: clamav-milter 1.0.9 at in-4.smtp.seeweb.it X-Virus-Status: Clean Subject: [LTP] [PATCH v2][STAGING] syscalls/fanotify26: Add test for nested permission events X-BeenThere: ltp@lists.linux.it X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Test Project List-Archive: List-Post: List-Help: List-Subscribe: , From: Edvard Conrad via ltp Reply-To: Edvard Conrad Cc: Amir Goldstein , Jan Kara , Edvard Conrad Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "ltp" The kernel creates the file descriptor it reports with a permission event by an open that must not generate further events. When the reported path is on a stacked filesystem, that open opens the real file on the backing filesystem, and since commit ebe559609d78 ("fs: get rid of __FMODE_NONOTIFY kludge") the backing file no longer inherits FMODE_NONOTIFY. A listener that also watches the backing filesystem is then sent a second permission event from inside its own read(2), which only the listener itself can answer, so a single reader never returns. Verify that a listener returns from read(2) and answers an open permission event for a file on an overlayfs mount. The first test case marks the overlay only and passes on any kernel, the second one also marks the backing filesystem, which is the shape an anti-malware scanner uses on an overlayfs root. The second case fails on a kernel without the pending fix "fs: let backing files inherit FMODE_NONOTIFY from the user file", so the test is added to runtest/staging for now. Link: https://lore.kernel.org/all/P4wV1J9--F-9@tuta.io/ Signed-off-by: Edvard Conrad --- v2: - Add the copyright header block. - Require FAN_MARK_FILESYSTEM support on the overlay and on the base mount in setup(). Both cases mark the overlay, so gating the check on the second case made the first one break instead of skip where the mark type is unsupported. - Report TPASS from the child that answers the event. Inferring it from the child reaching 'Z' took any abnormal exit for a success. - Use "!= -1" for file descriptor checks, and drop the redundant SAFE_CLOSE() before tst_brk() and the redundant fd_notify = -1. Thanks to the LTP AI reviewer for the review. runtest/staging | 1 + testcases/kernel/syscalls/fanotify/.gitignore | 1 + .../kernel/syscalls/fanotify/fanotify26.c | 185 ++++++++++++++++++ 3 files changed, 187 insertions(+) create mode 100644 testcases/kernel/syscalls/fanotify/fanotify26.c diff --git a/runtest/staging b/runtest/staging index ef1cdea15..2ce76b119 100644 --- a/runtest/staging +++ b/runtest/staging @@ -1 +1,2 @@ # Tests for features that are not yet in the stable kernel ABI +fanotify26 fanotify26 diff --git a/testcases/kernel/syscalls/fanotify/.gitignore b/testcases/kernel/syscalls/fanotify/.gitignore index d6d0599f1..c13d9b33c 100644 --- a/testcases/kernel/syscalls/fanotify/.gitignore +++ b/testcases/kernel/syscalls/fanotify/.gitignore @@ -23,4 +23,5 @@ /fanotify23 /fanotify24 /fanotify25 +/fanotify26 /fanotify_child diff --git a/testcases/kernel/syscalls/fanotify/fanotify26.c b/testcases/kernel/syscalls/fanotify/fanotify26.c new file mode 100644 index 000000000..4d7d6f1f5 --- /dev/null +++ b/testcases/kernel/syscalls/fanotify/fanotify26.c @@ -0,0 +1,185 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (c) 2026 Edvard Conrad + */ + +/*\ + * Check that a permission event on a stacked filesystem does not deadlock the + * :manpage:`fanotify(7)` listener. + * + * When the kernel reports a permission event, it creates the event file + * descriptor with an open that must not generate further events. If the + * reported path is on a stacked filesystem, that open opens the real file on + * the backing filesystem. Should the backing file not inherit "generate no + * events", and the listener watch the backing filesystem as well, the kernel + * queues a second permission event to the same group while the listener is + * still inside :manpage:`read(2)`. Only the listener can answer it, so a + * listener that reads with a single thread never returns, and every task that + * touches a watched filesystem queues up behind it. + * + * The first test case marks the overlay only and must pass on any kernel. The + * second one marks the backing filesystem as well, which is the shape an + * anti-malware scanner uses on an overlayfs root. + * + * The test needs root to create permission events and to mount overlayfs. + */ + +#define _GNU_SOURCE +#include "config.h" + +#include +#include +#include +#include +#include +#include +#include +#include +#include "tst_test.h" + +#ifdef HAVE_SYS_FANOTIFY_H +#include "fanotify.h" + +#define BACKING_MNT OVL_BASE_MNTPOINT +#define FNAME "test_file" +#define OVL_FILE OVL_MNT "/" FNAME +#define LOWER_FILE OVL_LOWER "/" FNAME + +/* + * The listener either answers the event at once or is blocked for good, so + * this only has to outlast scheduling noise on a loaded machine. + */ +#define WAIT_MSEC 5000 + +static int fd_notify = -1; + +static struct tcase { + const char *tname; + int mark_backing; +} tcases[] = { + {"Mark on the overlay", 0}, + {"Mark on the overlay and on the backing filesystem", 1}, +}; + +static void answer_one_event(void) +{ + struct fanotify_event_metadata event; + struct fanotify_response resp; + + /* Blocks for good if the event fd generates a nested event. */ + SAFE_READ(1, fd_notify, &event, sizeof(event)); + + if (event.mask != FAN_OPEN_PERM) { + tst_brk(TBROK, "Got unexpected event mask %llx", + (unsigned long long)event.mask); + } + + resp.fd = event.fd; + resp.response = FAN_ALLOW; + SAFE_WRITE(SAFE_WRITE_ALL, fd_notify, &resp, sizeof(resp)); + + if (event.fd != FAN_NOFD) + SAFE_CLOSE(event.fd); + + tst_res(TPASS, "Listener answered the event"); +} + +static void run(unsigned int n) +{ + struct tcase *tc = &tcases[n]; + pid_t opener, reader; + + tst_res(TINFO, "Test #%d: %s", n, tc->tname); + + fd_notify = SAFE_FANOTIFY_INIT(FAN_CLASS_CONTENT, O_RDONLY); + + SAFE_FANOTIFY_MARK(fd_notify, FAN_MARK_ADD | FAN_MARK_FILESYSTEM, + FAN_OPEN_PERM, AT_FDCWD, OVL_MNT); + + if (tc->mark_backing) { + SAFE_FANOTIFY_MARK(fd_notify, + FAN_MARK_ADD | FAN_MARK_FILESYSTEM, + FAN_OPEN_PERM, AT_FDCWD, BACKING_MNT); + } + + opener = SAFE_FORK(); + if (!opener) { + int fd; + + /* Must not hold the group, it has to be released on close. */ + SAFE_CLOSE(fd_notify); + /* + * The kernel denies the event when a listener that never + * answered it goes away, so a failure here is the fallout of + * the test tearing a blocked listener down, not a result. + */ + fd = open(OVL_FILE, O_RDONLY); + if (fd != -1) + SAFE_CLOSE(fd); + exit(0); + } + + /* The opener sleeps in the kernel once its event is queued. */ + if (TST_PROCESS_STATE_WAIT(opener, 'D', WAIT_MSEC)) + tst_brk(TBROK, "Open generated no permission event"); + + reader = SAFE_FORK(); + if (!reader) { + answer_one_event(); + exit(0); + } + + /* + * The listener answers and exits, or is blocked for good. Only the + * blocked case is handled here: the child reports its own success, + * so a child that died some other way cannot be taken for one that + * answered. The library reaps it on the normal path. + */ + if (TST_PROCESS_STATE_WAIT(reader, 'Z', WAIT_MSEC)) { + tst_res(TFAIL, + "Listener blocked in read() by a nested event"); + SAFE_KILL(reader, SIGKILL); + SAFE_WAITPID(reader, NULL, 0); + } + + /* Releases whatever is still queued, so the opener can finish. */ + SAFE_CLOSE(fd_notify); + + SAFE_WAITPID(opener, NULL, 0); +} + +static void setup(void) +{ + /* The file has to exist in the lower layer to be opened through it. */ + SAFE_UMOUNT(OVL_MNT); + SAFE_TOUCH(LOWER_FILE, 0644, NULL); + SAFE_MOUNT_OVERLAY(); + + require_fanotify_access_permissions_supported_on_fs(OVL_FILE); + + /* Every case marks the overlay; the second also marks the base. */ + REQUIRE_MARK_TYPE_SUPPORTED_ON_FS(FAN_MARK_FILESYSTEM, OVL_MNT); + REQUIRE_MARK_TYPE_SUPPORTED_ON_FS(FAN_MARK_FILESYSTEM, BACKING_MNT); +} + +static void cleanup(void) +{ + if (fd_notify != -1) + SAFE_CLOSE(fd_notify); +} + +static struct tst_test test = { + .test = run, + .tcnt = ARRAY_SIZE(tcases), + .setup = setup, + .cleanup = cleanup, + .forks_child = 1, + .needs_root = 1, + .mount_device = 1, + .needs_overlay = 1, + .mntpoint = OVL_BASE_MNTPOINT, +}; + +#else + TST_TEST_TCONF("system doesn't have required fanotify support"); +#endif -- 2.56.0 -- Mailing list info: https://lists.linux.it/listinfo/ltp