Subject: CVE-2024-39477: mm/hugetlb: do not call vma_add_reservation upon ENOMEM

From: Greg Kroah-Hartman <[email-masked]>

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

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

mm/hugetlb: do not call vma_add_reservation upon ENOMEM

sysbot reported a splat [1] on __unmap_hugepage_range().  This is because
vma_needs_reservation() can return -ENOMEM if
allocate_file_region_entries() fails to allocate the file_region struct
for the reservation.

Check for that and do not call vma_add_reservation() if that is the case,
otherwise region_abort() and region_del() will see that we do not have any
file_regions.

If we detect that vma_needs_reservation() returned -ENOMEM, we clear the
hugetlb_restore_reserve flag as if this reservation was still consumed, so
free_huge_folio() will not increment the resv count.

[1] https://lore.kernel.org/linux-mm/[email-masked]/T/#ma5983bc1ab18a54910da83416b3f89f3c7ee43aa

The Linux kernel CVE team has assigned CVE-2024-39477 to this issue.

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

	Issue introduced in 6.9 with commit df7a6d1f6405 and fixed in 6.9.5 with commit aa998f9dcb34
	Issue introduced in 6.9 with commit df7a6d1f6405 and fixed in 6.10 with commit 8daf9c702ee7

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-2024-39477
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/aa998f9dcb34c28448f86e8f5490f20d5eb0eac7
	https://git.kernel.org/stable/c/8daf9c702ee7f825f0de8600abff764acfedea13