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Date: Fri, 26 Sep 2008 17:19:11 -0400
From: Eric Paris <eparis@...hat.com>
To: linux-kernel@...r.kernel.org, malware-list@...ts.printk.net
Subject: [RFC 8/11] fanotify: ability for userspace to delay responses
fanotify: ability for userspace to delay responses
From: Eric Paris <eparis@...hat.com>
Userspace may know that it is behind, may know it is going to take a while
to get a good response, or have any number of other reasons to block an
access request. FAN_RESTTIMER will reset the timeout for an fanotify
access decision response.
Signed-off-by: Eric Paris <eparis@...hat.com>
---
fs/notify/access.c | 33 ++++++++++++++++++++++++++++-----
fs/notify/fanotify.h | 2 ++
fs/notify/notification.c | 2 ++
include/linux/fanotify.h | 5 +++--
4 files changed, 35 insertions(+), 7 deletions(-)
diff --git a/fs/notify/access.c b/fs/notify/access.c
index 132ef7b..b4b132b 100644
--- a/fs/notify/access.c
+++ b/fs/notify/access.c
@@ -56,6 +56,8 @@ int add_event_to_group_access(struct fanotify_group *group, struct fanotify_even
int get_response_from_group_access(struct fanotify_group *group, struct fanotify_event *event)
{
int ret;
+
+retry:
ret = wait_event_interruptible_timeout(group->access_waitq,
event->response,
msecs_to_jiffies(5000));
@@ -88,13 +90,25 @@ int get_response_from_group_access(struct fanotify_group *group, struct fanotify
}
/* userspace responded, convert to something usable */
+ spin_lock(&event->response_lock);
switch (event->response) {
case FAN_ALLOW:
- return 0;
+ ret = 0;
+ break;
case FAN_DENY:
+ ret = -EPERM;
+ break;
+ case FAN_RESETTIMER:
+ event->response = 0;
+ spin_unlock(&event->response_lock);
+ goto retry;
default:
- return -EPERM;
+ ret = -EPERM;
+ break;
}
+ spin_unlock(&event->response_lock);
+
+ return ret;
}
int fanotify_process_access_response(struct fanotify_group *group, unsigned long cookie, unsigned int response)
@@ -107,7 +121,7 @@ int fanotify_process_access_response(struct fanotify_group *group, unsigned long
* userspace can send a valid responce or we will clean it up after the
* timeout
*/
- if (response & ~(FAN_ALLOW | FAN_DENY))
+ if (response & ~(FAN_ALLOW | FAN_DENY | FAN_RESETTIMER))
return -EINVAL;
mutex_lock(&group->access_mutex);
@@ -116,11 +130,16 @@ int fanotify_process_access_response(struct fanotify_group *group, unsigned long
continue;
event = holder->event;
+
+ /* FAN_RESETTIMER should be left on the list for later.... */
+ if (response == FAN_RESETTIMER)
+ break;
+
holder->event = NULL;
/* as soon as we do this the event.holder might be reused */
list_del_init(&holder->event_list);
- if (event != (struct fanotify_event *)holder)
+ if (event != (struct fanotify_event *)holder)
destroy_event_holder(holder);
break;
}
@@ -129,9 +148,13 @@ int fanotify_process_access_response(struct fanotify_group *group, unsigned long
if (!event)
return -ENOENT;
+ spin_lock(&event->response_lock);
event->response = response;
+ spin_unlock(&event->response_lock);
wake_up(&group->access_waitq);
- put_event(event);
+
+ if (response != FAN_RESETTIMER)
+ put_event(event);
return 0;
}
diff --git a/fs/notify/fanotify.h b/fs/notify/fanotify.h
index 38e156e..cb97dbb 100644
--- a/fs/notify/fanotify.h
+++ b/fs/notify/fanotify.h
@@ -9,6 +9,7 @@
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/path.h>
+#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/wait.h>
@@ -74,6 +75,7 @@ struct fanotify_event {
atomic_t refcnt; /* how many groups still are using/need to send this event */
/* if waiting for a userspace access answer this is the cookie they will send back */
unsigned long cookie;
+ spinlock_t response_lock; /* protects response */
unsigned int response; /* userspace answer to question */
};
diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index e1a6a24..aa74137 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -25,6 +25,7 @@
#include <linux/path.h>
#include <linux/sched.h>
#include <linux/slab.h>
+#include <linux/spinlock.h>
#include <linux/fanotify.h>
#include "fanotify.h"
@@ -135,6 +136,7 @@ struct fanotify_event *create_event(struct file *file, unsigned int mask)
event->holder.event = NULL;
INIT_LIST_HEAD(&event->holder.event_list);
atomic_set(&event->refcnt, 1);
+ spin_lock_init(&event->response_lock);
event->path.dentry = file->f_path.dentry;
event->path.mnt = file->f_path.mnt;
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index 5d3e5d0..2a31e53 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -44,9 +44,10 @@
#define FAN_ALL_EVENTS_ACCESS (FAN_OPEN_ACCESS |\
FAN_READ_ACCESS)
-/* answers will need to be either allow or deny */
+/* answers will need to be either allow, deny, or reset */
#define FAN_ALLOW 0x00000001
-#define FAN_DENY 0x00000010
+#define FAN_DENY 0x00000002
+#define FAN_RESETTIMER 0x00000004
#ifdef __KERNEL__
--
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