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fanotify: use notification_lock instead of access_lock

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Fanotify code has its own lock (access_lock) to protect a list of events
waiting for a response from userspace.

However this is somewhat awkward as the same list_head in the event is
protected by notification_lock if it is part of the notification queue
and by access_lock if it is part of the fanotify private queue which
makes it difficult for any reliable checks in the generic code.  So make
fanotify use the same lock - notification_lock - for protecting its
private event list.

Link: http://lkml.kernel.org/r/1473797711-14111-6-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jan Kara 2016-10-07 16:56:55 -07:00 • committed by Linus Torvalds
parent c21dbe20f6
commit 073f65522a
2 changed files with 5 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

13
fs/notify/fanotify/fanotify_user.c
View file

@ -148,7 +148,7 @@ static struct fanotify_perm_event_info *dequeue_event(
{ {
struct fanotify_perm_event_info *event, *return_e = NULL; struct fanotify_perm_event_info *event, *return_e = NULL;
spin_lock(&group->fanotify_data.access_lock); spin_lock(&group->notification_lock);
list_for_each_entry(event, &group->fanotify_data.access_list, list_for_each_entry(event, &group->fanotify_data.access_list,
fae.fse.list) { fae.fse.list) {
if (event->fd != fd) if (event->fd != fd)
@ -158,7 +158,7 @@ static struct fanotify_perm_event_info *dequeue_event(
return_e = event; return_e = event;
break; break;
} }
spin_unlock(&group->fanotify_data.access_lock); spin_unlock(&group->notification_lock);
pr_debug("%s: found return_re=%p\n", __func__, return_e); pr_debug("%s: found return_re=%p\n", __func__, return_e);
@ -310,10 +310,10 @@ static ssize_t fanotify_read(struct file *file, char __user *buf,
wake_up(&group->fanotify_data.access_waitq); wake_up(&group->fanotify_data.access_waitq);
break; break;
} }
spin_lock(&group->fanotify_data.access_lock); spin_lock(&group->notification_lock);
list_add_tail(&kevent->list, list_add_tail(&kevent->list,
&group->fanotify_data.access_list); &group->fanotify_data.access_list);
spin_unlock(&group->fanotify_data.access_lock); spin_unlock(&group->notification_lock);
#endif #endif
} }
buf += ret; buf += ret;
@ -372,7 +372,7 @@ static int fanotify_release(struct inode *ignored, struct file *file)
* Process all permission events on access_list and notification queue * Process all permission events on access_list and notification queue
* and simulate reply from userspace. * and simulate reply from userspace.
*/ */
spin_lock(&group->fanotify_data.access_lock); spin_lock(&group->notification_lock);
list_for_each_entry_safe(event, next, &group->fanotify_data.access_list, list_for_each_entry_safe(event, next, &group->fanotify_data.access_list,
fae.fse.list) { fae.fse.list) {
pr_debug("%s: found group=%p event=%p\n", __func__, group, pr_debug("%s: found group=%p event=%p\n", __func__, group,
@ -381,14 +381,12 @@ static int fanotify_release(struct inode *ignored, struct file *file)
list_del_init(&event->fae.fse.list); list_del_init(&event->fae.fse.list);
event->response = FAN_ALLOW; event->response = FAN_ALLOW;
} }
spin_unlock(&group->fanotify_data.access_lock);
/* /*
* Destroy all non-permission events. For permission events just * Destroy all non-permission events. For permission events just
* dequeue them and set the response. They will be freed once the * dequeue them and set the response. They will be freed once the
* response is consumed and fanotify_get_response() returns. * response is consumed and fanotify_get_response() returns.
*/ */
spin_lock(&group->notification_lock);
while (!fsnotify_notify_queue_is_empty(group)) { while (!fsnotify_notify_queue_is_empty(group)) {
fsn_event = fsnotify_remove_first_event(group); fsn_event = fsnotify_remove_first_event(group);
if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) { if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) {
@ -768,7 +766,6 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
event_f_flags |= O_LARGEFILE; event_f_flags |= O_LARGEFILE;
group->fanotify_data.f_flags = event_f_flags; group->fanotify_data.f_flags = event_f_flags;
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
spin_lock_init(&group->fanotify_data.access_lock);
init_waitqueue_head(&group->fanotify_data.access_waitq); init_waitqueue_head(&group->fanotify_data.access_waitq);
INIT_LIST_HEAD(&group->fanotify_data.access_list); INIT_LIST_HEAD(&group->fanotify_data.access_list);
#endif #endif

1
include/linux/fsnotify_backend.h
View file

@ -177,7 +177,6 @@ struct fsnotify_group {
struct fanotify_group_private_data { struct fanotify_group_private_data {
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
/* allows a group to block waiting for a userspace response */ /* allows a group to block waiting for a userspace response */
spinlock_t access_lock;
struct list_head access_list; struct list_head access_list;
wait_queue_head_t access_waitq; wait_queue_head_t access_waitq;
#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */ #endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */