Re: [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



* David Hildenbrand:

> On 19.01.23 22:23, Rick Edgecombe wrote:
>> The x86 Control-flow Enforcement Technology (CET) feature includes a new
>> type of memory called shadow stack. This shadow stack memory has some
>> unusual properties, which requires some core mm changes to function
>> properly.
>> Shadow stack memory is writable only in very specific, controlled
>> ways.
>> However, since it is writable, the kernel treats it as such. As a result
>> there remain many ways for userspace to trigger the kernel to write to
>> shadow stack's via get_user_pages(, FOLL_WRITE) operations. To make this a
>> little less exposed, block writable GUPs for shadow stack VMAs.
>> Still allow FOLL_FORCE to write through shadow stack protections, as
>> it
>> does for read-only protections.
>
> So an app can simply modify the shadow stack itself by writing to
> /proc/self/mem ?
>
> Is that really intended? Looks like security hole to me at first
> sight, but maybe I am missing something important.

Isn't it possible to overwrite GOT pointers using the same vector?
So I think it's merely reflecting the status quo.

Thanks,
Florian




[Index of Archives]     [Linux Kernel]     [Kernel Newbies]     [x86 Platform Driver]     [Netdev]     [Linux Wireless]     [Netfilter]     [Bugtraq]     [Linux Filesystems]     [Yosemite Discussion]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Device Mapper]

  Powered by Linux