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ovl: fix warning in ovl_create_real()

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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>
This commit is contained in:
Miklos Szeredi 2021-11-04 10:55:34 +01:00
parent 9a25440376
commit 1f5573cfe7
3 changed files with 10 additions and 6 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

3
fs/overlayfs/dir.c
View file

@ -137,8 +137,7 @@ int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
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;

1
fs/overlayfs/overlayfs.h
View file

@ -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);

12
fs/overlayfs/super.c
View file

@ -787,10 +787,14 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
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: