From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f66.google.com ([74.125.82.66]:55111 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932356AbdJYIls (ORCPT ); Wed, 25 Oct 2017 04:41:48 -0400 Received: by mail-wm0-f66.google.com with SMTP id r68so325540wmr.3 for ; Wed, 25 Oct 2017 01:41:47 -0700 (PDT) From: Miklos Szeredi To: linux-fsdevel@vger.kernel.org Cc: Jan Kara , Amir Goldstein , Xiong Zhou , linux-kernel@vger.kernel.org Subject: [PATCH v2 5/7] fanotify: fix fsnotify_prepare_user_wait() failure Date: Wed, 25 Oct 2017 10:41:37 +0200 Message-Id: <1508920899-8115-6-git-send-email-mszeredi@redhat.com> In-Reply-To: <1508920899-8115-1-git-send-email-mszeredi@redhat.com> References: <1508920899-8115-1-git-send-email-mszeredi@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: If fsnotify_prepare_user_wait() fails, we leave the event on the notification list. Which will result in a warning in fsnotify_destroy_event() and later use-after-free. Instead of adding a new helper to remove the event from the list in this case, I opted to move the prepare/finish up into fanotify_handle_event(). This will allow these to be moved further out into the generic code later, and perhaps let us move to non-sleeping RCU. Signed-off-by: Miklos Szeredi Fixes: 05f0e38724e8 ("fanotify: Release SRCU lock when waiting for userspace response") Cc: # v4.12 --- fs/notify/fanotify/fanotify.c | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-) diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index 2fa99aeaa095..df3f484e458a 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -64,19 +64,8 @@ static int fanotify_get_response(struct fsnotify_group *group, pr_debug("%s: group=%p event=%p\n", __func__, group, event); - /* - * fsnotify_prepare_user_wait() fails if we race with mark deletion. - * Just let the operation pass in that case. - */ - if (!fsnotify_prepare_user_wait(iter_info)) { - event->response = FAN_ALLOW; - goto out; - } - wait_event(group->fanotify_data.access_waitq, event->response); - fsnotify_finish_user_wait(iter_info); -out: /* userspace responded, convert to something usable */ switch (event->response) { case FAN_ALLOW: @@ -211,9 +200,21 @@ static int fanotify_handle_event(struct fsnotify_group *group, pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, mask); +#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS + if (mask & FAN_ALL_PERM_EVENTS) { + /* + * fsnotify_prepare_user_wait() fails if we race with mark + * deletion. Just let the operation pass in that case. + */ + if (!fsnotify_prepare_user_wait(iter_info)) + return 0; + } +#endif + event = fanotify_alloc_event(inode, mask, data); + ret = -ENOMEM; if (unlikely(!event)) - return -ENOMEM; + goto finish; fsn_event = &event->fse; ret = fsnotify_add_event(group, fsn_event, fanotify_merge); @@ -223,7 +224,8 @@ static int fanotify_handle_event(struct fsnotify_group *group, /* Our event wasn't used in the end. Free it. */ fsnotify_destroy_event(group, fsn_event); - return 0; + ret = 0; + goto finish; } #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS @@ -232,6 +234,11 @@ static int fanotify_handle_event(struct fsnotify_group *group, iter_info); fsnotify_destroy_event(group, fsn_event); } +finish: + if (mask & FAN_ALL_PERM_EVENTS) + fsnotify_finish_user_wait(iter_info); +#else +finish: #endif return ret; } -- 2.5.5