Re: kernel BUG at mm/hugetlb.c:LINE!

[Colin Walters]

On Tue, May 12, 2020, at 11:04 AM, Miklos Szeredi wrote:

> > However, in this syzbot test case the 'file' is in an overlayfs filesystem
> > created as follows:
> >
> > mkdir("./file0", 000)                   = 0
> > mount(NULL, "./file0", "hugetlbfs", MS_MANDLOCK|MS_POSIXACL, NULL) = 0
> > chdir("./file0")                        = 0
> > mkdir("./file1", 000)                   = 0
> > mkdir("./bus", 000)                     = 0
> > mkdir("./file0", 000)                   = 0
> > mount("\177ELF\2\1\1", "./bus", "overlay", 0, "lowerdir=./bus,workdir=./file1,u"...) = 0

Is there any actual valid use case for mounting an overlayfs on top of hugetlbfs?  I can't think of one.  Why isn't the response to this to instead only allow mounting overlayfs on top of basically a set of whitelisted filesystems?