syzbot excercised the forbidden practice of moving the workdir under
lowerdir while overlayfs is mounted and tripped a dentry reference leak.
Fixes: c63e56a4a652 ("ovl: do not open/llseek lower file with upper sb_writers held")
Reported-and-tested-by: syzbot+8608bb4553edb8c78f41@syzkaller.appspotmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
path.dentry = temp;
err = ovl_copy_up_data(c, &path);
/*
path.dentry = temp;
err = ovl_copy_up_data(c, &path);
/*
- * We cannot hold lock_rename() throughout this helper, because or
+ * We cannot hold lock_rename() throughout this helper, because of
* lock ordering with sb_writers, which shouldn't be held when calling
* ovl_copy_up_data(), so lock workdir and destdir and make sure that
* temp wasn't moved before copy up completion or cleanup.
* lock ordering with sb_writers, which shouldn't be held when calling
* ovl_copy_up_data(), so lock workdir and destdir and make sure that
* temp wasn't moved before copy up completion or cleanup.
- * If temp was moved, abort without the cleanup.
*/
ovl_start_write(c->dentry);
if (lock_rename(c->workdir, c->destdir) != NULL ||
temp->d_parent != c->workdir) {
*/
ovl_start_write(c->dentry);
if (lock_rename(c->workdir, c->destdir) != NULL ||
temp->d_parent != c->workdir) {
+ /* temp or workdir moved underneath us? abort without cleanup */
+ dput(temp);
err = -EIO;
goto unlock;
} else if (err) {
err = -EIO;
goto unlock;
} else if (err) {