From: Miklos Szeredi mszeredi@redhat.com
commit 1f5573cfe7a7056e80a92c7a037a3e69f3a13d1c upstream.
Syzbot triggered the following warning in ovl_workdir_create() -> ovl_create_real():
if (!err && WARN_ON(!newdentry->d_inode)) {
The reason is that the cgroup2 filesystem returns from mkdir without instantiating the new dentry.
Weird filesystems such as this will be rejected by overlayfs at a later stage during setup, but to prevent such a warning, call ovl_mkdir_real() directly from ovl_workdir_create() and reject this case early.
Reported-and-tested-by: syzbot+75eab84fd0af9e8bf66b@syzkaller.appspotmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/overlayfs/dir.c | 3 +-- fs/overlayfs/overlayfs.h | 1 + fs/overlayfs/super.c | 12 ++++++++---- 3 files changed, 10 insertions(+), 6 deletions(-)
--- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -137,8 +137,7 @@ kill_whiteout: goto out; }
-static int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry, - umode_t mode) +int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry, umode_t mode) { int err; struct dentry *d, *dentry = *newdentry; --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -570,6 +570,7 @@ struct ovl_cattr {
#define OVL_CATTR(m) (&(struct ovl_cattr) { .mode = (m) })
+int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry, umode_t mode); struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry, struct ovl_cattr *attr); int ovl_cleanup(struct inode *dir, struct dentry *dentry); --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -787,10 +787,14 @@ retry: goto retry; }
- work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode)); - err = PTR_ERR(work); - if (IS_ERR(work)) - goto out_err; + err = ovl_mkdir_real(dir, &work, attr.ia_mode); + if (err) + goto out_dput; + + /* Weird filesystem returning with hashed negative (kernfs)? */ + err = -EINVAL; + if (d_really_is_negative(work)) + goto out_dput;
/* * Try to remove POSIX ACL xattrs from workdir. We are good if: