From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44C0FC433EF for ; Sat, 20 Nov 2021 17:13:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237712AbhKTRQD (ORCPT ); Sat, 20 Nov 2021 12:16:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231557AbhKTRQC (ORCPT ); Sat, 20 Nov 2021 12:16:02 -0500 Received: from mail-wr1-x432.google.com (mail-wr1-x432.google.com [IPv6:2a00:1450:4864:20::432]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 233BAC061574 for ; Sat, 20 Nov 2021 09:12:59 -0800 (PST) Received: by mail-wr1-x432.google.com with SMTP id d5so24056661wrc.1 for ; Sat, 20 Nov 2021 09:12:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=dWzGfdwEXwvgGylNgZmFPq2hdBBrBuejNX8fZbP35Hk=; b=gJTsYyPA/R9ZhgXlaVzUzdCXYYug/eyclOiJPUo2GZ7u2puL2b9bmjt0/mnWpD3WIl lxWFOBXZ2D5m541u3x5W8q4a5kNG7/ob8gFm8nE9+Eqn6aDKnM4JXqYyOaFPaMJUWa7r cx4itWW1GSN0vzivQaJBIxvBxMOEmfMIzfvN5BIYcvTKPrdEa2sQ6rzVLrAH84LFJ9uM jfaVCaih0LojELihknWFPyPd0UrgDg6TFzci52aJHcwPeAaZivioWnQ7iQMpTnB17xVh DZh8oBvzWLRtXZHloqEOetdbWOYR7sLvPYFO4uuHhs5+4RAKmdG56BJTv2BJr9uaNt2O bK/A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=dWzGfdwEXwvgGylNgZmFPq2hdBBrBuejNX8fZbP35Hk=; b=UXD36QRVhAC0YxbKtxDzZZ6qURav0mQrELhEuBwrQ5ZLDIEd/B70LfiUi3HCKhX6rD Gy+NH+aGD8DCqukGm7JIHMDPyUZXO8Qj6R2imLOqy0afCXDtqS9soa9UFpk/fR9ffkQ7 q8Ersjbq7ohEbt/jXYkUq2S2/8YAWHnRhyHujlvXMbC9yA31bA6ZI3t2G/SDz5/ETnQf qIyE3NsCOydYb1BWcV2WgXmiK6tNAU8mOYAh3pfU92qaDogU9nqDhMTaoN0BX+Dt87nl SYjvQ300VtM53fuPI/oAQE5/CHjXAqpaOYNQnWzP+qwaSSA+QuxJu0bFIWkrkqIFMyzB tpDw== X-Gm-Message-State: AOAM533TkIDZDVwWIr1LddiEX8Bj4hffY7ZSUsf/8FW0piDoOP8r31DW MYfLTmoIAU0E5ehAW4m1O7A/5p//3Bw= X-Google-Smtp-Source: ABdhPJwAbwYF0fl8AOy81d7asgTQIUaN0Yf5U7wR4tEbF2qfHn/vF00B3e3IHjCuDE4XbtOPZC4VVw== X-Received: by 2002:a5d:64e7:: with SMTP id g7mr20155472wri.350.1637428377244; Sat, 20 Nov 2021 09:12:57 -0800 (PST) Received: from localhost.localdomain ([82.114.45.86]) by smtp.gmail.com with ESMTPSA id n8sm3108829wrp.95.2021.11.20.09.12.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 20 Nov 2021 09:12:56 -0800 (PST) From: Amir Goldstein To: Alejandro Colomar Cc: Michael Kerrisk , Jan Kara , Matthew Bobrowski , linux-man@vger.kernel.org Subject: [PATCH v2 1/4] fanotify_init.2, fanotify_mark.2: Document unprivileged listener Date: Sat, 20 Nov 2021 19:12:50 +0200 Message-Id: <20211120171253.1385863-2-amir73il@gmail.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211120171253.1385863-1-amir73il@gmail.com> References: <20211120171253.1385863-1-amir73il@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org From: Matthew Bobrowski Document the limited fanotify functionality that will be available for unprivileged users from kernel v5.13. Signed-off-by: Matthew Bobrowski Signed-off-by: Amir Goldstein --- man2/fanotify_init.2 | 77 +++++++++++++++++++++++++++++++++++++------- man2/fanotify_mark.2 | 9 ++++++ 2 files changed, 74 insertions(+), 12 deletions(-) diff --git a/man2/fanotify_init.2 b/man2/fanotify_init.2 index 2b44fc6ec..b2ceb17f3 100644 --- a/man2/fanotify_init.2 +++ b/man2/fanotify_init.2 @@ -57,15 +57,6 @@ In the current implementation, the number of fanotify groups per user is limited to 128. This limit cannot be overridden. .PP -Calling -.BR fanotify_init () -requires the -.B CAP_SYS_ADMIN -capability. -This constraint might be relaxed in future versions of the API. -Therefore, certain additional capability checks have been implemented as -indicated below. -.PP The .I flags argument contains a multi-bit field defining the notification class of the @@ -86,6 +77,9 @@ It is intended for event listeners that need to access files before they contain their final data. This notification class might be used by hierarchical storage managers, for example. +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .B FAN_CLASS_CONTENT This value allows the receipt of events notifying that a file has been @@ -94,6 +88,9 @@ It is intended for event listeners that need to access files when they already contain their final content. This notification class might be used by malware detection programs, for example. +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .B FAN_CLASS_NOTIF This is the default value. @@ -155,6 +152,9 @@ supplied to .BR read (2) (see .BR fanotify (7)). +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .BR FAN_ENABLE_AUDIT " (since Linux 4.15)" .\" commit de8cd83e91bc3ee212b3e6ec6e4283af9e4ab269 @@ -163,6 +163,9 @@ permission events. The permission event response has to be marked with the .B FAN_AUDIT flag for an audit log record to be generated. +Use of this flag requires the +.B CAP_AUDIT_WRITE +capability. .TP .BR FAN_REPORT_FID " (since Linux 5.1)" .\" commit a8b13aa20afb69161b5123b4f1acc7ea0a03d360 @@ -378,13 +381,63 @@ The fanotify API is available only if the kernel was configured with .BR CONFIG_FANOTIFY . .TP .B EPERM -The operation is not permitted because the caller lacks the -.B CAP_SYS_ADMIN -capability. +The operation is not permitted because the caller lacks a required capability. .SH VERSIONS .BR fanotify_init () was introduced in version 2.6.36 of the Linux kernel and enabled in version 2.6.37. +.PP +Prior to Linux 5.13, +.\" commit 7cea2a3c505e87a9d6afc78be4a7f7be636a73a7 +calling +.BR fanotify_init () +required the +.B CAP_SYS_ADMIN +capability. +Since Linux 5.13, +.\" commit 7cea2a3c505e87a9d6afc78be4a7f7be636a73a7 +users may call +.BR fanotify_init () +without the +.B CAP_SYS_ADMIN +capability to create and intialize an fanotify group with limited functionality. +.TP +The limitations imposed on an event listener created by a user without the +.B CAP_SYS_ADMIN +capability are as follows: +.RS +.IP * 3 +The user cannot request for an unlimited event queue by using +.BR FAN_UNLIMITED_QUEUE . +.IP * 3 +The user cannot request for an unlimited number of marks by using +.BR FAN_UNLIMITED_MARKS . +.IP * 3 +The user cannot request to use either notification classes +.BR FAN_CLASS_CONTENT +or +.BR FAN_CLASS_PRE_CONTENT . +This means that user cannot request permission events. +.IP * 3 +The user is required to create a group that identifies filesystem objects by +file handles, for example, by providing the +.BR FAN_REPORT_FID +flag. +.IP * 3 +The user is limited to only mark inodes. +The ability to mark a mount or filesystem via +.BR fanotify_mark() +through the use of +.BR FAN_MARK_MOUNT +or +.BR FAN_MARK_FILESYSTEM +is not permitted. +.IP * 3 +The event object in the event queue is limited in terms of the information +that is made available to the unprivileged user. +A user will also not receive the pid that generated the event, unless the +listening process itself generated the event. +.RE .SH CONFORMING TO This system call is Linux-specific. .SH BUGS diff --git a/man2/fanotify_mark.2 b/man2/fanotify_mark.2 index 036f56ebf..9cf71320c 100644 --- a/man2/fanotify_mark.2 +++ b/man2/fanotify_mark.2 @@ -142,6 +142,9 @@ contains Attempting to do so will result in the error .B EINVAL being returned. +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .BR FAN_MARK_FILESYSTEM " (since Linux 4.20)" .\" commit d54f4fba889b205e9cd8239182ca5d27d0ac3bc2 @@ -152,6 +155,9 @@ The filesystem containing will be marked. All the contained files and directories of the filesystem from any mount point will be monitored. +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .B FAN_MARK_IGNORED_MASK The events in @@ -454,6 +460,9 @@ handles. This error can be returned only with an fanotify group that identifies filesystem objects by file handles. .TP +.B EPERM +The operation is not permitted because the caller lacks a required capability. +.TP .B EXDEV The filesystem object indicated by .I pathname -- 2.33.1