On Tue 04-12-18 15:44:46, Kees Cook wrote:
> As a precaution, make sure we check event_len when copying to userspace.
> Based on old feedback: https://lkml.kernel.org/r/542d9fe5.3010...@gmx.de
>
> Signed-off-by: Kees Cook <keesc...@chromium.org>
Thanks for the patch, I've added it to my tree.
Honza
> ---
> fs/notify/fanotify/fanotify_user.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c
> b/fs/notify/fanotify/fanotify_user.c
> index e03be5071362..d9484a0ac6b3 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -206,7 +206,7 @@ static int process_access_response(struct fsnotify_group
> *group,
>
> static ssize_t copy_event_to_user(struct fsnotify_group *group,
> struct fsnotify_event *event,
> - char __user *buf)
> + char __user *buf, size_t count)
> {
> struct fanotify_event_metadata fanotify_event_metadata;
> struct file *f;
> @@ -220,6 +220,12 @@ static ssize_t copy_event_to_user(struct fsnotify_group
> *group,
>
> fd = fanotify_event_metadata.fd;
> ret = -EFAULT;
> + /*
> + * Sanity check copy size in case get_one_event() and
> + * fill_event_metadata() event_len sizes ever get out of sync.
> + */
> + if (WARN_ON_ONCE(fanotify_event_metadata.event_len > count))
> + goto out_close_fd;
> if (copy_to_user(buf, &fanotify_event_metadata,
> fanotify_event_metadata.event_len))
> goto out_close_fd;
> @@ -295,7 +301,7 @@ static ssize_t fanotify_read(struct file *file, char
> __user *buf,
> continue;
> }
>
> - ret = copy_event_to_user(group, kevent, buf);
> + ret = copy_event_to_user(group, kevent, buf, count);
> if (unlikely(ret == -EOPENSTALE)) {
> /*
> * We cannot report events with stale fd so drop it.
> --
> 2.17.1
>
>
> --
> Kees Cook
--
Jan Kara <j...@suse.com>
SUSE Labs, CR
