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 X-Spam-Level: X-Spam-Status: No, score=-6.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ADEF7C2BB85 for ; Thu, 16 Apr 2020 12:17:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 87D8420767 for ; Thu, 16 Apr 2020 12:17:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="g9l2+EXK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2635206AbgDPMRB (ORCPT ); Thu, 16 Apr 2020 08:17:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S2635123AbgDPMQx (ORCPT ); Thu, 16 Apr 2020 08:16:53 -0400 Received: from mail-vk1-xa41.google.com (mail-vk1-xa41.google.com [IPv6:2607:f8b0:4864:20::a41]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23F9CC061A0F; Thu, 16 Apr 2020 05:16:53 -0700 (PDT) Received: by mail-vk1-xa41.google.com with SMTP id v129so1809336vkf.10; Thu, 16 Apr 2020 05:16:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:reply-to:from:date:message-id :subject:to:cc; bh=AqeflJ58xwYJZoUpJFfKMREP6pT62WKOOgkRpGZL13E=; b=g9l2+EXKA/5dMtP982E81okunHnJ8x1yDPK0hAsuMXLKzr4p8+zanQnWeOz+vCys5m F9uxBBEOoc6kh80ZGMHgIFdsNpwph8sD5StBcknzDH3Y4sym028M/T44GGWL0wwG/+50 2oQjFGzJGakKy79cExPa7EjppiXBLF+xTRrKYPH++fAcq615lBr3OOdhMwiQ8jVhe5JH Iyv7/E/Hh97124MG4ggGJb7WGjyHEsLlsuJ+YbRuaotqCNDEMDhOT2L5dIAJ11fjhB78 T+9eSrK3M6vbPBrjCzYtAtV0ofs1/HjXCreFZ421nGB7vQFv2GwZbQnfp9y5EOynS9kA tLLA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:reply-to :from:date:message-id:subject:to:cc; bh=AqeflJ58xwYJZoUpJFfKMREP6pT62WKOOgkRpGZL13E=; b=FoB1eQop6vAmjjDaONdFaHyPNYejIOYzRHhbx38cBZwXMdiEa2GX5B9vmrbto9Qn5/ UKHvByTXwzfR9bKpPpKJ9C2K6XHnO+DHuwFH+psU0J1CQeOCYsj1P7r2kTtjpSP14R2M p+CsZ6SVeG3XLkRvpSYGJkC43GYryWhyw0q8BB7hJWOcBOG5DKwQTK+S/E8ZLF8k6PMb TJavKHS1R/kz0Dnx7e31OaQFXgFHIA+PLt97mM5YwPPuqjgi65utHZvHqU/5TNMqxs8z 3P/lG6hH02zdTWaRenABKjYZ3XHcpN+1AY0wIXdMNb0HaPDc1RXv3jYJNXNYLno0Ag2C lPjQ== X-Gm-Message-State: AGi0PuZJGOorIlesVxB4bauiWKYP9Osc41i3WvwNthhHXQAW2VlWwQUl piWZLTZKILtsvajLdwKFoYcR2jBIS1tqliktK7c= X-Google-Smtp-Source: APiQypKNFO+EYVOguq6GITNTHS/7qOhF2tsWfMdJ1n+uVmWLZ07cyLbSF3pU+dM3JF01xadH5H9o5zrIGIzn4RVb9po= X-Received: by 2002:a1f:1fc7:: with SMTP id f190mr22135857vkf.84.1587039412066; Thu, 16 Apr 2020 05:16:52 -0700 (PDT) MIME-Version: 1.0 References: <20200217131455.31107-1-amir73il@gmail.com> <20200217131455.31107-14-amir73il@gmail.com> In-Reply-To: <20200217131455.31107-14-amir73il@gmail.com> Reply-To: mtk.manpages@gmail.com From: "Michael Kerrisk (man-pages)" Date: Thu, 16 Apr 2020 14:16:40 +0200 Message-ID: Subject: Re: [PATCH v2 13/16] fanotify: report name info for FAN_DIR_MODIFY event To: Amir Goldstein Cc: Jan Kara , "linux-fsdevel@vger.kernel.org" , Linux API , Michael Kerrisk Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Hello Amir, On Mon, 17 Feb 2020 at 15:10, Amir Goldstein wrote: > > Report event FAN_DIR_MODIFY with name in a variable length record similar > to how fid's are reported. With name info reporting implemented, setting > FAN_DIR_MODIFY in mark mask is now allowed. I see this was merged for 5.7. Would you be able to send a man-pages patch that documents this new feature please. Cheers, Michael > > When events are reported with name, the reported fid identifies the > directory and the name follows the fid. The info record type for this > event info is FAN_EVENT_INFO_TYPE_DFID_NAME. > > For now, all reported events have at most one info record which is > either FAN_EVENT_INFO_TYPE_FID or FAN_EVENT_INFO_TYPE_DFID_NAME (for > FAN_DIR_MODIFY). Later on, events "on child" will report both records. > > There are several ways that an application can use this information: > > 1. When watching a single directory, the name is always relative to > the watched directory, so application need to fstatat(2) the name > relative to the watched directory. > > 2. When watching a set of directories, the application could keep a map > of dirfd for all watched directories and hash the map by fid obtained > with name_to_handle_at(2). When getting a name event, the fid in the > event info could be used to lookup the base dirfd in the map and then > call fstatat(2) with that dirfd. > > 3. When watching a filesystem (FAN_MARK_FILESYSTEM) or a large set of > directories, the application could use open_by_handle_at(2) with the fid > in event info to obtain dirfd for the directory where event happened and > call fstatat(2) with this dirfd. > > The last option scales better for a large number of watched directories. > The first two options may be available in the future also for non > privileged fanotify watchers, because open_by_handle_at(2) requires > the CAP_DAC_READ_SEARCH capability. > > Signed-off-by: Amir Goldstein > --- > fs/notify/fanotify/fanotify.c | 2 +- > fs/notify/fanotify/fanotify_user.c | 120 ++++++++++++++++++++++------- > include/linux/fanotify.h | 3 +- > include/uapi/linux/fanotify.h | 1 + > 4 files changed, 98 insertions(+), 28 deletions(-) > > diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c > index fc75dc53a218..b651c18d3a93 100644 > --- a/fs/notify/fanotify/fanotify.c > +++ b/fs/notify/fanotify/fanotify.c > @@ -478,7 +478,7 @@ static int fanotify_handle_event(struct fsnotify_group *group, > BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC); > BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM); > > - BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 19); > + BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 20); > > mask = fanotify_group_event_mask(group, iter_info, mask, data, > data_type); > diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c > index 284f3548bb79..a1bafc21ebbb 100644 > --- a/fs/notify/fanotify/fanotify_user.c > +++ b/fs/notify/fanotify/fanotify_user.c > @@ -51,20 +51,32 @@ struct kmem_cache *fanotify_name_event_cachep __read_mostly; > struct kmem_cache *fanotify_perm_event_cachep __read_mostly; > > #define FANOTIFY_EVENT_ALIGN 4 > +#define FANOTIFY_INFO_HDR_LEN \ > + (sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle)) > > -static int fanotify_fid_info_len(struct fanotify_fid_hdr *fh) > +static int fanotify_fid_info_len(int fh_len, int name_len) > { > - return roundup(sizeof(struct fanotify_event_info_fid) + > - sizeof(struct file_handle) + fh->len, > - FANOTIFY_EVENT_ALIGN); > + int info_len = fh_len; > + > + if (name_len) > + info_len += name_len + 1; > + > + return roundup(FANOTIFY_INFO_HDR_LEN + info_len, FANOTIFY_EVENT_ALIGN); > } > > static int fanotify_event_info_len(struct fanotify_event *event) > { > - if (!fanotify_event_has_fid(event)) > - return 0; > + int info_len = 0; > + > + if (fanotify_event_has_fid(event)) > + info_len += fanotify_fid_info_len(event->fh.len, 0); > + > + if (fanotify_event_has_dfid_name(event)) { > + info_len += fanotify_fid_info_len(event->dfh.len, > + fanotify_event_name_len(event)); > + } > > - return fanotify_fid_info_len(&event->fh); > + return info_len; > } > > /* > @@ -210,23 +222,34 @@ static int process_access_response(struct fsnotify_group *group, > return -ENOENT; > } > > -static int copy_fid_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh, > - struct fanotify_fid *fid, char __user *buf) > +static int copy_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh, > + struct fanotify_fid *fid, const struct qstr *name, > + char __user *buf, size_t count) > { > struct fanotify_event_info_fid info = { }; > struct file_handle handle = { }; > - unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *data; > + unsigned char bounce[max(FANOTIFY_INLINE_FH_LEN, DNAME_INLINE_LEN)]; > + const unsigned char *data; > size_t fh_len = fh->len; > - size_t len = fanotify_fid_info_len(fh); > + size_t name_len = name ? name->len : 0; > + size_t info_len = fanotify_fid_info_len(fh_len, name_len); > + size_t len = info_len; > + > + pr_debug("%s: fh_len=%lu name_len=%lu, info_len=%lu, count=%lu\n", > + __func__, fh_len, name_len, info_len, count); > > - if (!len) > + if (!fh_len || (name && !name_len)) > return 0; > > - if (WARN_ON_ONCE(len < sizeof(info) + sizeof(handle) + fh_len)) > + if (WARN_ON_ONCE(len < sizeof(info) || len > count)) > return -EFAULT; > > - /* Copy event info fid header followed by vaiable sized file handle */ > - info.hdr.info_type = FAN_EVENT_INFO_TYPE_FID; > + /* > + * Copy event info fid header followed by vaiable sized file handle > + * and optionally followed by vaiable sized filename. > + */ > + info.hdr.info_type = name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME : > + FAN_EVENT_INFO_TYPE_FID; > info.hdr.len = len; > info.fsid = *fsid; > if (copy_to_user(buf, &info, sizeof(info))) > @@ -234,6 +257,9 @@ static int copy_fid_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh, > > buf += sizeof(info); > len -= sizeof(info); > + if (WARN_ON_ONCE(len < sizeof(handle))) > + return -EFAULT; > + > handle.handle_type = fh->type; > handle.handle_bytes = fh_len; > if (copy_to_user(buf, &handle, sizeof(handle))) > @@ -241,9 +267,12 @@ static int copy_fid_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh, > > buf += sizeof(handle); > len -= sizeof(handle); > + if (WARN_ON_ONCE(len < fh_len)) > + return -EFAULT; > + > /* > - * For an inline fh, copy through stack to exclude the copy from > - * usercopy hardening protections. > + * For an inline fh and inline file name, copy through stack to exclude > + * the copy from usercopy hardening protections. > */ > data = fanotify_fid_fh(fid, fh_len); > if (fh_len <= FANOTIFY_INLINE_FH_LEN) { > @@ -253,14 +282,33 @@ static int copy_fid_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh, > if (copy_to_user(buf, data, fh_len)) > return -EFAULT; > > - /* Pad with 0's */ > buf += fh_len; > len -= fh_len; > + > + if (name_len) { > + /* Copy the filename with terminating null */ > + name_len++; > + if (WARN_ON_ONCE(len < name_len)) > + return -EFAULT; > + > + data = name->name; > + if (name_len <= DNAME_INLINE_LEN) { > + memcpy(bounce, data, name_len); > + data = bounce; > + } > + if (copy_to_user(buf, data, name_len)) > + return -EFAULT; > + > + buf += name_len; > + len -= name_len; > + } > + > + /* Pad with 0's */ > WARN_ON_ONCE(len < 0 || len >= FANOTIFY_EVENT_ALIGN); > if (len > 0 && clear_user(buf, len)) > return -EFAULT; > > - return 0; > + return info_len; > } > > static ssize_t copy_event_to_user(struct fsnotify_group *group, > @@ -282,12 +330,12 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, > metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS; > metadata.pid = pid_vnr(event->pid); > > - if (fanotify_event_has_path(event)) { > + if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) { > + metadata.event_len += fanotify_event_info_len(event); > + } else if (fanotify_event_has_path(event)) { > fd = create_fd(group, event, &f); > if (fd < 0) > return fd; > - } else if (fanotify_event_has_fid(event)) { > - metadata.event_len += fanotify_event_info_len(event); > } > metadata.fd = fd; > > @@ -302,16 +350,36 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, > if (copy_to_user(buf, &metadata, FAN_EVENT_METADATA_LEN)) > goto out_close_fd; > > + buf += FAN_EVENT_METADATA_LEN; > + count -= FAN_EVENT_METADATA_LEN; > + > if (fanotify_is_perm_event(event->mask)) > FANOTIFY_PE(fsn_event)->fd = fd; > > - if (fanotify_event_has_path(event)) { > + if (f) > fd_install(fd, f); > - } else if (fanotify_event_has_fid(event)) { > - ret = copy_fid_to_user(&event->fsid, &event->fh, &event->fid, > - buf + FAN_EVENT_METADATA_LEN); > + > + /* Event info records order is: dir fid + name, child fid */ > + if (fanotify_event_has_dfid_name(event)) { > + struct fanotify_name_event *fne = FANOTIFY_NE(fsn_event); > + > + ret = copy_info_to_user(&event->fsid, &event->dfh, &fne->dfid, > + &fne->name, buf, count); > if (ret < 0) > return ret; > + > + buf += ret; > + count -= ret; > + } > + > + if (fanotify_event_has_fid(event)) { > + ret = copy_info_to_user(&event->fsid, &event->fh, &event->fid, > + NULL, buf, count); > + if (ret < 0) > + return ret; > + > + buf += ret; > + count -= ret; > } > > return metadata.event_len; > diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h > index b79fa9bb7359..3049a6c06d9e 100644 > --- a/include/linux/fanotify.h > +++ b/include/linux/fanotify.h > @@ -47,7 +47,8 @@ > * Directory entry modification events - reported only to directory > * where entry is modified and not to a watching parent. > */ > -#define FANOTIFY_DIRENT_EVENTS (FAN_MOVE | FAN_CREATE | FAN_DELETE) > +#define FANOTIFY_DIRENT_EVENTS (FAN_MOVE | FAN_CREATE | FAN_DELETE | \ > + FAN_DIR_MODIFY) > > /* Events that can only be reported with data type FSNOTIFY_EVENT_INODE */ > #define FANOTIFY_INODE_EVENTS (FANOTIFY_DIRENT_EVENTS | \ > diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h > index 615fa2c87179..2b56e194b858 100644 > --- a/include/uapi/linux/fanotify.h > +++ b/include/uapi/linux/fanotify.h > @@ -117,6 +117,7 @@ struct fanotify_event_metadata { > }; > > #define FAN_EVENT_INFO_TYPE_FID 1 > +#define FAN_EVENT_INFO_TYPE_DFID_NAME 2 > > /* Variable length info record following event metadata */ > struct fanotify_event_info_header { > -- > 2.17.1 > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/