Subject: CVE-2024-47676: mm/hugetlb.c: fix UAF of vma in hugetlb fault pathway

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

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

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

mm/hugetlb.c: fix UAF of vma in hugetlb fault pathway

Syzbot reports a UAF in hugetlb_fault().  This happens because
vmf_anon_prepare() could drop the per-VMA lock and allow the current VMA
to be freed before hugetlb_vma_unlock_read() is called.

We can fix this by using a modified version of vmf_anon_prepare() that
doesn't release the VMA lock on failure, and then release it ourselves
after hugetlb_vma_unlock_read().

The Linux kernel CVE team has assigned CVE-2024-47676 to this issue.

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

	Issue introduced in 6.9 with commit 9acad7ba3e25 and fixed in 6.10.13 with commit e897d184a8dd
	Issue introduced in 6.9 with commit 9acad7ba3e25 and fixed in 6.11.2 with commit d59ebc99dee0
	Issue introduced in 6.9 with commit 9acad7ba3e25 and fixed in 6.12-rc1 with commit 98b74bb4d7e9

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-2024-47676
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/e897d184a8dd4a4e1f39c8c495598e4d9472776c
	https://git.kernel.org/stable/c/d59ebc99dee0a2687a26df94b901eb8216dbf876
	https://git.kernel.org/stable/c/98b74bb4d7e96b4da5ef3126511febe55b76b807