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fanotify: sanitize failure exits in copy_event_to_user()

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* do copy_to_user() before prepare_for_access_response(); that kills
the need in remove_access_response().
* don't do fd_install() until we are past the last possible failure
exit.  Don't use sys_close() on cleanup side - just put_unused_fd()
and fput().  Less racy that way...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2012-08-19 12:30:45 -04:00
commit 352e3b2492
1 changed files with 20 additions and 39 deletions
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59
fs/notify/fanotify/fanotify_user.c
View file

@ -58,7 +58,9 @@ static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
return fsnotify_remove_notify_event(group);
}
static int create_fd(struct fsnotify_group *group, struct fsnotify_event *event)
static int create_fd(struct fsnotify_group *group,
struct fsnotify_event *event,
struct file **file)
{
int client_fd;
struct file *new_file;
@ -98,7 +100,7 @@ static int create_fd(struct fsnotify_group *group, struct fsnotify_event *event)
put_unused_fd(client_fd);
client_fd = PTR_ERR(new_file);
} else {
fd_install(client_fd, new_file);
*file = new_file;
}
return client_fd;
@ -106,13 +108,15 @@ static int create_fd(struct fsnotify_group *group, struct fsnotify_event *event)
static int fill_event_metadata(struct fsnotify_group *group,
struct fanotify_event_metadata *metadata,
struct fsnotify_event *event)
struct fsnotify_event *event,
struct file **file)
{
int ret = 0;
pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
group, metadata, event);
*file = NULL;
metadata->event_len = FAN_EVENT_METADATA_LEN;
metadata->metadata_len = FAN_EVENT_METADATA_LEN;
metadata->vers = FANOTIFY_METADATA_VERSION;
@ -121,7 +125,7 @@ static int fill_event_metadata(struct fsnotify_group *group,
if (unlikely(event->mask & FAN_Q_OVERFLOW))
metadata->fd = FAN_NOFD;
else {
metadata->fd = create_fd(group, event);
metadata->fd = create_fd(group, event, file);
if (metadata->fd < 0)
ret = metadata->fd;
}
@ -220,25 +224,6 @@ static int prepare_for_access_response(struct fsnotify_group *group,
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,
@ -247,12 +232,6 @@ static int prepare_for_access_response(struct fsnotify_group *group,
return 0;
}
static void remove_access_response(struct fsnotify_group *group,
struct fsnotify_event *event,
__s32 fd)
{
return;
}
#endif
static ssize_t copy_event_to_user(struct fsnotify_group *group,
@ -260,31 +239,33 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
char __user *buf)
{
struct fanotify_event_metadata fanotify_event_metadata;
struct file *f;
int fd, ret;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
ret = fill_event_metadata(group, &fanotify_event_metadata, event);
ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
if (ret < 0)
goto out;
fd = fanotify_event_metadata.fd;
ret = -EFAULT;
if (copy_to_user(buf, &fanotify_event_metadata,
fanotify_event_metadata.event_len))
goto out_close_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,
fanotify_event_metadata.event_len))
goto out_kill_access_response;
fd_install(fd, f);
return fanotify_event_metadata.event_len;
out_kill_access_response:
remove_access_response(group, event, fd);
out_close_fd:
if (fd != FAN_NOFD)
sys_close(fd);
if (fd != FAN_NOFD) {
put_unused_fd(fd);
fput(f);
}
out:
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
if (event->mask & FAN_ALL_PERM_EVENTS) {