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fanotify: permissions and blocking

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This is the backend work needed for fanotify to support the new
FS_OPEN_PERM and FS_ACCESS_PERM fsnotify events.  This is done using the
new fsnotify secondary queue.  No userspace interface is provided actually
respond to or request these events.

Signed-off-by: Eric Paris <eparis@redhat.com>
This commit is contained in:
Eric Paris
2009-12-17 21:24:34 -05:00
parent c4ec54b40d
commit 9e66e4233d
5 changed files with 99 additions and 4 deletions
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14
fs/notify/fanotify/Kconfig
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@@ -10,3 +10,17 @@ config FANOTIFY
the event.
If unsure, say Y.
config FANOTIFY_ACCESS_PERMISSIONS
bool "fanotify permissions checking"
depends on FANOTIFY
depends on SECURITY
default n
---help---
Say Y here is you want fanotify listeners to be able to make permissions
decisions concerning filesystem events. This is used by some fanotify
listeners which need to scan files before allowing the system access to
use those files. This is used by some anti-malware vendors and by some
hierarchical storage managent systems.
If unsure, say N.

54
fs/notify/fanotify/fanotify.c
View File

@@ -2,9 +2,12 @@
#include <linux/fdtable.h>
#include <linux/fsnotify_backend.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/kernel.h> /* UINT_MAX */
#include <linux/mount.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/wait.h>
static bool should_merge(struct fsnotify_event *old, struct fsnotify_event *new)
{
@@ -88,10 +91,37 @@ out:
return ret;
}
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
static int fanotify_get_response_from_access(struct fsnotify_group *group,
struct fsnotify_event *event)
{
int ret;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
wait_event(group->fanotify_data.access_waitq, event->response);
/* userspace responded, convert to something usable */
spin_lock(&event->lock);
switch (event->response) {
case FAN_ALLOW:
ret = 0;
break;
case FAN_DENY:
default:
ret = -EPERM;
}
event->response = 0;
spin_unlock(&event->lock);
return ret;
}
#endif
static int fanotify_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
{
int ret;
struct fsnotify_event *used_event;
struct fsnotify_event *notify_event = NULL;
BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
@@ -100,15 +130,31 @@ static int fanotify_handle_event(struct fsnotify_group *group, struct fsnotify_e
BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
ret = fsnotify_add_notify_event(group, event, NULL, fanotify_merge, (void **)&used_event);
ret = fsnotify_add_notify_event(group, event, NULL, fanotify_merge,
(void **)&notify_event);
/* -EEXIST means this event was merged with another, not that it was an error */
if (ret == -EEXIST)
ret = 0;
if (used_event)
fsnotify_put_event(used_event);
if (ret)
goto out;
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
if (event->mask & FAN_ALL_PERM_EVENTS) {
/* if we merged we need to wait on the new event */
if (notify_event)
event = notify_event;
ret = fanotify_get_response_from_access(group, event);
}
#endif
out:
if (notify_event)
fsnotify_put_event(notify_event);
return ret;
}

5
fs/notify/fanotify/fanotify_user.c
View File

@@ -482,6 +482,11 @@ SYSCALL_DEFINE3(fanotify_init, unsigned int, flags, unsigned int, event_f_flags,
return PTR_ERR(group);
group->priority = priority;
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
mutex_init(&group->fanotify_data.access_mutex);
init_waitqueue_head(&group->fanotify_data.access_waitq);
INIT_LIST_HEAD(&group->fanotify_data.access_list);
#endif
fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
if (fd < 0)