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fanotify: Make sure to check event_len when copying 

As a precaution, make sure we check event_len when copying to userspace.
Based on old feedback: https://lkml.kernel.org/r/542D9FE5.3010009@gmx.de

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Kees Cook 2018-12-04 15:44:46 -08:00 committed by Jan Kara
parent d6f7aa9820
commit 5b03a472b4
1 changed files with 8 additions and 2 deletions
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10
fs/notify/fanotify/fanotify_user.c
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@ -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.