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fanotify: Track permission event state

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Track whether permission event got already reported to userspace and
whether userspace already answered to the permission event. Protect
stores to this field together with updates to ->response field by
group->notification_lock. This will allow aborting wait for reply to
permission event from userspace.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jan Kara 2019-01-08 14:02:44 +01:00
parent ca6f86998d
commit 40873284d7
3 changed files with 40 additions and 11 deletions
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6
fs/notify/fanotify/fanotify.c
View file

@ -85,7 +85,8 @@ 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->response);
wait_event(group->fanotify_data.access_waitq,
event->state == FAN_EVENT_ANSWERED);
/* userspace responded, convert to something usable */
switch (event->response & ~FAN_AUDIT) {
@ -101,8 +102,6 @@ static int fanotify_get_response(struct fsnotify_group *group,
if (event->response & FAN_AUDIT)
audit_fanotify(event->response & ~FAN_AUDIT);
event->response = 0;
pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
group, event, ret);
@ -275,6 +274,7 @@ struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
goto out;
event = &pevent->fae;
pevent->response = 0;
pevent->state = FAN_EVENT_INIT;
goto init;
}
event = kmem_cache_alloc(fanotify_event_cachep, gfp);

10
fs/notify/fanotify/fanotify.h
View file

@ -8,6 +8,13 @@ extern struct kmem_cache *fanotify_mark_cache;
extern struct kmem_cache *fanotify_event_cachep;
extern struct kmem_cache *fanotify_perm_event_cachep;
/* Possible states of the permission event */
enum {
FAN_EVENT_INIT,
FAN_EVENT_REPORTED,
FAN_EVENT_ANSWERED
};
/*
* 3 dwords are sufficient for most local fs (64bit ino, 32bit generation).
* For 32bit arch, fid increases the size of fanotify_event by 12 bytes and
@ -109,7 +116,8 @@ static inline void *fanotify_event_fh(struct fanotify_event *event)
*/
struct fanotify_perm_event {
struct fanotify_event fae;
int response; /* userspace answer to question */
unsigned short response; /* userspace answer to the event */
unsigned short state; /* state of the event */
int fd; /* fd we passed to userspace for this event */
};

35
fs/notify/fanotify/fanotify_user.c
View file

@ -64,7 +64,8 @@ static int fanotify_event_info_len(struct fanotify_event *event)
/*
* Get an fsnotify notification event if one exists and is small
* enough to fit in "count". Return an error pointer if the count
* is not large enough.
* is not large enough. When permission event is dequeued, its state is
* updated accordingly.
*/
static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
size_t count)
@ -88,6 +89,8 @@ static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
goto out;
}
fsn_event = fsnotify_remove_first_event(group);
if (fanotify_is_perm_event(FANOTIFY_E(fsn_event)->mask))
FANOTIFY_PE(fsn_event)->state = FAN_EVENT_REPORTED;
out:
spin_unlock(&group->notification_lock);
return fsn_event;
@ -135,6 +138,21 @@ static int create_fd(struct fsnotify_group *group,
return client_fd;
}
/*
* Finish processing of permission event by setting it to ANSWERED state and
* drop group->notification_lock.
*/
static void finish_permission_event(struct fsnotify_group *group,
struct fanotify_perm_event *event,
unsigned int response)
__releases(&group->notification_lock)
{
assert_spin_locked(&group->notification_lock);
event->response = response;
event->state = FAN_EVENT_ANSWERED;
spin_unlock(&group->notification_lock);
}
static int process_access_response(struct fsnotify_group *group,
struct fanotify_response *response_struct)
{
@ -170,8 +188,7 @@ static int process_access_response(struct fsnotify_group *group,
continue;
list_del_init(&event->fae.fse.list);
event->response = response;
spin_unlock(&group->notification_lock);
finish_permission_event(group, event, response);
wake_up(&group->fanotify_data.access_waitq);
return 0;
}
@ -354,7 +371,9 @@ static ssize_t fanotify_read(struct file *file, char __user *buf,
fsnotify_destroy_event(group, kevent);
} else {
if (ret <= 0) {
FANOTIFY_PE(kevent)->response = FAN_DENY;
spin_lock(&group->notification_lock);
finish_permission_event(group,
FANOTIFY_PE(kevent), FAN_DENY);
wake_up(&group->fanotify_data.access_waitq);
} else {
spin_lock(&group->notification_lock);
@ -423,7 +442,8 @@ static int fanotify_release(struct inode *ignored, struct file *file)
event = list_first_entry(&group->fanotify_data.access_list,
struct fanotify_perm_event, fae.fse.list);
list_del_init(&event->fae.fse.list);
event->response = FAN_ALLOW;
finish_permission_event(group, event, FAN_ALLOW);
spin_lock(&group->notification_lock);
}
/*
@ -436,10 +456,11 @@ static int fanotify_release(struct inode *ignored, struct file *file)
if (!(FANOTIFY_E(fsn_event)->mask & FANOTIFY_PERM_EVENTS)) {
spin_unlock(&group->notification_lock);
fsnotify_destroy_event(group, fsn_event);
spin_lock(&group->notification_lock);
} else {
FANOTIFY_PE(fsn_event)->response = FAN_ALLOW;
finish_permission_event(group, FANOTIFY_PE(fsn_event),
FAN_ALLOW);
}
spin_lock(&group->notification_lock);
}
spin_unlock(&group->notification_lock);