CVE-2024-36000: mm/hugetlb: fix missing hugetlb_lock for resv uncharge

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

mm/hugetlb: fix missing hugetlb_lock for resv uncharge

There is a recent report on UFFDIO_COPY over hugetlb:

https://lore.kernel.org/all/000000000000ee06de0616177560@google.com/

350:	lockdep_assert_held(&hugetlb_lock);

Should be an issue in hugetlb but triggered in an userfault context, where
it goes into the unlikely path where two threads modifying the resv map
together.  Mike has a fix in that path for resv uncharge but it looks like
the locking criteria was overlooked: hugetlb_cgroup_uncharge_folio_rsvd()
will update the cgroup pointer, so it requires to be called with the lock
held.

The Linux kernel CVE team has assigned CVE-2024-36000 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.10 with commit 79aa925bf239 and fixed in 6.1.91 with commit 4c806333efea
	Issue introduced in 5.10 with commit 79aa925bf239 and fixed in 6.6.30 with commit f6c5d21db16a
	Issue introduced in 5.10 with commit 79aa925bf239 and fixed in 6.8.9 with commit 538faabf31e9
	Issue introduced in 5.10 with commit 79aa925bf239 and fixed in 6.9 with commit b76b46902c2d
	Issue introduced in 5.9.7 with commit f87004c0b2bd

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-36000
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	mm/hugetlb.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/4c806333efea1000a2a9620926f560ad2e1ca7cc
	https://git.kernel.org/stable/c/f6c5d21db16a0910152ec8aa9d5a7aed72694505
	https://git.kernel.org/stable/c/538faabf31e9c53d8c870d114846fda958a0de10
	https://git.kernel.org/stable/c/b76b46902c2d0395488c8412e1116c2486cdfcb2