linux-cve-announce - CVE-2022-50446: ARC: mm: fix leakage of memory allocated for PTE

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Message-ID: <2025100115-CVE-2022-50446-94be@gregkh>
Date: Wed,  1 Oct 2025 13:45:16 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50446: ARC: mm: fix leakage of memory allocated for PTE

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

ARC: mm: fix leakage of memory allocated for PTE

Since commit d9820ff ("ARC: mm: switch pgtable_t back to struct page *")
a memory leakage problem occurs. Memory allocated for page table entries
not released during process termination. This issue can be reproduced by
a small program that allocates a large amount of memory. After several
runs, you'll see that the amount of free memory has reduced and will
continue to reduce after each run. All ARC CPUs are effected by this
issue. The issue was introduced since the kernel stable release v5.15-rc1.

As described in commit d9820ff after switch pgtable_t back to struct
page *, a pointer to "struct page" and appropriate functions are used to
allocate and free a memory page for PTEs, but the pmd_pgtable macro hasn't
changed and returns the direct virtual address from the PMD (PGD) entry.
Than this address used as a parameter in the __pte_free() and as a result
this function couldn't release memory page allocated for PTEs.

Fix this issue by changing the pmd_pgtable macro and returning pointer to
struct page.

The Linux kernel CVE team has assigned CVE-2022-50446 to this issue.

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

	Issue introduced in 5.15 with commit d9820ff76f95fa26d33e412254a89cd65b23142d and fixed in 5.15.77 with commit 14009ada5712649589ab4ad0441b811780ea8773
	Issue introduced in 5.15 with commit d9820ff76f95fa26d33e412254a89cd65b23142d and fixed in 6.0.7 with commit d83a69966e8b6ae9dd447f3ac704c0223bceb7f7
	Issue introduced in 5.15 with commit d9820ff76f95fa26d33e412254a89cd65b23142d and fixed in 6.1 with commit 4fd9df10cb7a9289fbd22d669f9f98164d95a1ce

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-2022-50446
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:
	arch/arc/include/asm/pgtable-levels.h

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/14009ada5712649589ab4ad0441b811780ea8773
	https://git.kernel.org/stable/c/d83a69966e8b6ae9dd447f3ac704c0223bceb7f7
	https://git.kernel.org/stable/c/4fd9df10cb7a9289fbd22d669f9f98164d95a1ce