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authorJan Kara <jack@suse.cz>2014-01-28 18:29:24 +0100
committerJan Kara <jack@suse.cz>2014-01-29 13:57:04 +0100
commit13116dfd13c8c9d60ea04ece13419af2de8e2e37 (patch)
treebad7a21d6c43925fe4e7102f9816847ed133e775 /fs/notify
parent0e47c969c65e213421450c31043353ebe3c67e0c (diff)
downloadlinux-linaro-stable-13116dfd13c8c9d60ea04ece13419af2de8e2e37.tar.gz
fanotify: Fix use after free in mask checking
We cannot use the event structure returned from fsnotify_add_notify_event() because that event can be freed by the time that function returns. Use the mask argument passed into the event handler directly instead. This also fixes a possible problem when we could unnecessarily wait for permission response for a normal fanotify event which got merged with a permission event. We also disallow merging of permission event with any other event so that we know the permission event which we just created is the one on which we should wait for permission response. Reported-and-tested-by: Jiri Kosina <jkosina@suse.cz> Reported-and-tested-by: Dave Jones <davej@fedoraproject.org> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/notify')
-rw-r--r--fs/notify/fanotify/fanotify.c21
1 files changed, 11 insertions, 10 deletions
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 58772623f02a..cc78e2fbc8e4 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -16,12 +16,6 @@ static bool should_merge(struct fsnotify_event *old_fsn,
{
struct fanotify_event_info *old, *new;
-#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
- /* dont merge two permission events */
- if ((old_fsn->mask & FAN_ALL_PERM_EVENTS) &&
- (new_fsn->mask & FAN_ALL_PERM_EVENTS))
- return false;
-#endif
pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
old = FANOTIFY_E(old_fsn);
new = FANOTIFY_E(new_fsn);
@@ -42,6 +36,16 @@ static struct fsnotify_event *fanotify_merge(struct list_head *list,
pr_debug("%s: list=%p event=%p\n", __func__, list, event);
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+ /*
+ * Don't merge a permission event with any other event so that we know
+ * the event structure we have created in fanotify_handle_event() is the
+ * one we should check for permission response.
+ */
+ if (event->mask & FAN_ALL_PERM_EVENTS)
+ return NULL;
+#endif
+
list_for_each_entry_reverse(test_event, list, list) {
if (should_merge(test_event, event)) {
do_merge = true;
@@ -195,13 +199,10 @@ static int fanotify_handle_event(struct fsnotify_group *group,
fsnotify_destroy_event(group, fsn_event);
if (IS_ERR(notify_fsn_event))
return PTR_ERR(notify_fsn_event);
- /* We need to ask about a different events after a merge... */
- event = FANOTIFY_E(notify_fsn_event);
- fsn_event = notify_fsn_event;
}
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
- if (fsn_event->mask & FAN_ALL_PERM_EVENTS)
+ if (mask & FAN_ALL_PERM_EVENTS)
ret = fanotify_get_response_from_access(group, event);
#endif
return ret;