Commit b2d87909 authored by Eric Paris's avatar Eric Paris
Browse files

fanotify: userspace interface for permission responses



fanotify groups need to respond to events which include permissions types.
To do so groups will send a response using write() on the fanotify_fd they
have open.
Signed-off-by: default avatarEric Paris <eparis@redhat.com>
parent 9e66e423
......@@ -114,6 +114,9 @@ static int fanotify_get_response_from_access(struct fsnotify_group *group,
event->response = 0;
spin_unlock(&event->lock);
pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
group, event, ret);
return ret;
}
#endif
......
......@@ -18,6 +18,13 @@
extern const struct fsnotify_ops fanotify_fsnotify_ops;
static struct kmem_cache *fanotify_mark_cache __read_mostly;
static struct kmem_cache *fanotify_response_event_cache __read_mostly;
struct fanotify_response_event {
struct list_head list;
__s32 fd;
struct fsnotify_event *event;
};
/*
* Get an fsnotify notification event if one exists and is small
......@@ -110,23 +117,152 @@ static ssize_t fill_event_metadata(struct fsnotify_group *group,
return metadata->fd;
}
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
static struct fanotify_response_event *dequeue_re(struct fsnotify_group *group,
__s32 fd)
{
struct fanotify_response_event *re, *return_re = NULL;
mutex_lock(&group->fanotify_data.access_mutex);
list_for_each_entry(re, &group->fanotify_data.access_list, list) {
if (re->fd != fd)
continue;
list_del_init(&re->list);
return_re = re;
break;
}
mutex_unlock(&group->fanotify_data.access_mutex);
pr_debug("%s: found return_re=%p\n", __func__, return_re);
return return_re;
}
static int process_access_response(struct fsnotify_group *group,
struct fanotify_response *response_struct)
{
struct fanotify_response_event *re;
__s32 fd = response_struct->fd;
__u32 response = response_struct->response;
pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
fd, response);
/*
* make sure the response is valid, if invalid we do nothing and either
* userspace can send a valid responce or we will clean it up after the
* timeout
*/
switch (response) {
case FAN_ALLOW:
case FAN_DENY:
break;
default:
return -EINVAL;
}
if (fd < 0)
return -EINVAL;
re = dequeue_re(group, fd);
if (!re)
return -ENOENT;
re->event->response = response;
wake_up(&group->fanotify_data.access_waitq);
kmem_cache_free(fanotify_response_event_cache, re);
return 0;
}
static int prepare_for_access_response(struct fsnotify_group *group,
struct fsnotify_event *event,
__s32 fd)
{
struct fanotify_response_event *re;
if (!(event->mask & FAN_ALL_PERM_EVENTS))
return 0;
re = kmem_cache_alloc(fanotify_response_event_cache, GFP_KERNEL);
if (!re)
return -ENOMEM;
re->event = event;
re->fd = fd;
mutex_lock(&group->fanotify_data.access_mutex);
list_add_tail(&re->list, &group->fanotify_data.access_list);
mutex_unlock(&group->fanotify_data.access_mutex);
return 0;
}
static void remove_access_response(struct fsnotify_group *group,
struct fsnotify_event *event,
__s32 fd)
{
struct fanotify_response_event *re;
if (!(event->mask & FAN_ALL_PERM_EVENTS))
return;
re = dequeue_re(group, fd);
if (!re)
return;
BUG_ON(re->event != event);
kmem_cache_free(fanotify_response_event_cache, re);
return;
}
#else
static int prepare_for_access_response(struct fsnotify_group *group,
struct fsnotify_event *event,
__s32 fd)
{
return 0;
}
static void remove_access_response(struct fsnotify_group *group,
struct fsnotify_event *event,
__s32 fd)
{
return 0;
}
#endif
static ssize_t copy_event_to_user(struct fsnotify_group *group,
struct fsnotify_event *event,
char __user *buf)
{
struct fanotify_event_metadata fanotify_event_metadata;
int ret;
int fd, ret;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
ret = fill_event_metadata(group, &fanotify_event_metadata, event);
if (ret < 0)
return ret;
fd = fill_event_metadata(group, &fanotify_event_metadata, event);
if (fd < 0)
return fd;
ret = prepare_for_access_response(group, event, fd);
if (ret)
goto out_close_fd;
ret = -EFAULT;
if (copy_to_user(buf, &fanotify_event_metadata, FAN_EVENT_METADATA_LEN))
return -EFAULT;
goto out_kill_access_response;
return FAN_EVENT_METADATA_LEN;
out_kill_access_response:
remove_access_response(group, event, fd);
out_close_fd:
sys_close(fd);
return ret;
}
/* intofiy userspace file descriptor functions */
......@@ -197,6 +333,33 @@ static ssize_t fanotify_read(struct file *file, char __user *buf,
return ret;
}
static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
{
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
struct fanotify_response response = { .fd = -1, .response = -1 };
struct fsnotify_group *group;
int ret;
group = file->private_data;
if (count > sizeof(response))
count = sizeof(response);
pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
if (copy_from_user(&response, buf, count))
return -EFAULT;
ret = process_access_response(group, &response);
if (ret < 0)
count = ret;
return count;
#else
return -EINVAL;
#endif
}
static int fanotify_release(struct inode *ignored, struct file *file)
{
struct fsnotify_group *group = file->private_data;
......@@ -237,6 +400,7 @@ static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long ar
static const struct file_operations fanotify_fops = {
.poll = fanotify_poll,
.read = fanotify_read,
.write = fanotify_write,
.fasync = NULL,
.release = fanotify_release,
.unlocked_ioctl = fanotify_ioctl,
......@@ -470,7 +634,7 @@ SYSCALL_DEFINE3(fanotify_init, unsigned int, flags, unsigned int, event_f_flags,
if (flags & ~FAN_ALL_INIT_FLAGS)
return -EINVAL;
f_flags = (O_RDONLY | FMODE_NONOTIFY);
f_flags = O_RDWR | FMODE_NONOTIFY;
if (flags & FAN_CLOEXEC)
f_flags |= O_CLOEXEC;
if (flags & FAN_NONBLOCK)
......@@ -527,7 +691,11 @@ SYSCALL_DEFINE(fanotify_mark)(int fanotify_fd, unsigned int flags,
default:
return -EINVAL;
}
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
#else
if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
#endif
return -EINVAL;
filp = fget_light(fanotify_fd, &fput_needed);
......@@ -600,6 +768,8 @@ SYSCALL_ALIAS(sys_fanotify_mark, SyS_fanotify_mark);
static int __init fanotify_user_setup(void)
{
fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
fanotify_response_event_cache = KMEM_CACHE(fanotify_response_event,
SLAB_PANIC);
return 0;
}
......
......@@ -75,6 +75,11 @@ struct fanotify_event_metadata {
__s64 pid;
} __attribute__ ((packed));
struct fanotify_response {
__s32 fd;
__u32 response;
} __attribute__ ((packed));
/* Legit userspace responses to a _PERM event */
#define FAN_ALLOW 0x01
#define FAN_DENY 0x02
......
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