From patchwork Wed Feb 13 14:54:43 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 10810101 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C66181390 for ; Wed, 13 Feb 2019 14:55:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 780832D35F for ; Wed, 13 Feb 2019 14:55:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6CCEF2D5C1; Wed, 13 Feb 2019 14:55:02 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F0E092D3C0 for ; Wed, 13 Feb 2019 14:55:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403937AbfBMOzA (ORCPT ); Wed, 13 Feb 2019 09:55:00 -0500 Received: from mx2.suse.de ([195.135.220.15]:60294 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2403928AbfBMOy7 (ORCPT ); Wed, 13 Feb 2019 09:54:59 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 2EA52AE27; Wed, 13 Feb 2019 14:54:56 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 621291E41F4; Wed, 13 Feb 2019 15:54:54 +0100 (CET) From: Jan Kara To: Cc: Amir Goldstein , Konstantin Khlebnikov , Vivek Trivedi , Orion Poplawski , Jan Kara Subject: [PATCH 6/6] fanotify: Use interruptible wait when waiting for permission events Date: Wed, 13 Feb 2019 15:54:43 +0100 Message-Id: <20190213145443.26836-7-jack@suse.cz> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20190213145443.26836-1-jack@suse.cz> References: <20190213145443.26836-1-jack@suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When waiting for response to fanotify permission events, we currently use uninterruptible waits. That makes code simple however it can cause lots of processes to end up in uninterruptible sleep with hard reboot being the only alternative in case fanotify listener process stops responding (e.g. due to a bug in its implementation). Uninterruptible sleep also makes system hibernation fail if the listener gets frozen before the process generating fanotify permission event. Fix these problems by using interruptible sleep for waiting for response to fanotify event. This is slightly tricky though - we have to detect when the event got already reported to userspace as in that case we must not free the event. Instead we push the responsibility for freeing the event to the process that will write response to the event. Reported-by: Orion Poplawski Reported-by: Konstantin Khlebnikov Signed-off-by: Jan Kara Reviewed-by: Amir Goldstein --- fs/notify/fanotify/fanotify.c | 35 ++++++++++++++++++++++++++++++++--- fs/notify/fanotify/fanotify.h | 3 ++- 2 files changed, 34 insertions(+), 4 deletions(-) diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index e725831be161..2e40d5d8660b 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -57,6 +57,13 @@ static int fanotify_merge(struct list_head *list, struct fsnotify_event *event) return 0; } +/* + * Wait for response to permission event. The function also takes care of + * freeing the permission event (or offloads that in case the wait is canceled + * by a signal). The function returns 0 in case access got allowed by userspace, + * -EPERM in case userspace disallowed the access, and -ERESTARTSYS in case + * the wait got interrupted by a signal. + */ static int fanotify_get_response(struct fsnotify_group *group, struct fanotify_perm_event_info *event, struct fsnotify_iter_info *iter_info) @@ -65,8 +72,29 @@ static int fanotify_get_response(struct fsnotify_group *group, pr_debug("%s: group=%p event=%p\n", __func__, group, event); - wait_event(group->fanotify_data.access_waitq, - event->state == FAN_EVENT_ANSWERED); + ret = wait_event_interruptible(group->fanotify_data.access_waitq, + event->state == FAN_EVENT_ANSWERED); + /* Signal pending? */ + if (ret < 0) { + spin_lock(&group->notification_lock); + /* Event reported to userspace and no answer yet? */ + if (event->state == FAN_EVENT_REPORTED) { + /* Event will get freed once userspace answers to it */ + event->state = FAN_EVENT_CANCELED; + spin_unlock(&group->notification_lock); + return ret; + } + /* Event not yet reported? Just remove it. */ + if (event->state == FAN_EVENT_INIT) + fsnotify_remove_queued_event(group, &event->fae.fse); + /* + * Event may be also answered in case signal delivery raced + * with wakeup. In that case we have nothing to do besides + * freeing the event and reporting error. + */ + spin_unlock(&group->notification_lock); + goto out; + } /* userspace responded, convert to something usable */ switch (event->response & ~FAN_AUDIT) { @@ -84,6 +112,8 @@ static int fanotify_get_response(struct fsnotify_group *group, pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, group, event, ret); +out: + fsnotify_destroy_event(group, &event->fae.fse); return ret; } @@ -255,7 +285,6 @@ static int fanotify_handle_event(struct fsnotify_group *group, } else if (fanotify_is_perm_event(mask)) { ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event), iter_info); - fsnotify_destroy_event(group, fsn_event); } finish: if (fanotify_is_perm_event(mask)) diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h index 98d58939777c..bbdd2adfbf0f 100644 --- a/fs/notify/fanotify/fanotify.h +++ b/fs/notify/fanotify/fanotify.h @@ -26,7 +26,8 @@ struct fanotify_event_info { enum { FAN_EVENT_INIT, FAN_EVENT_REPORTED, - FAN_EVENT_ANSWERED + FAN_EVENT_ANSWERED, + FAN_EVENT_CANCELED, }; /*