Subject: CVE-2024-41021: s390/mm: Fix VM_FAULT_HWPOISON handling in do_exception()

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

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

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

s390/mm: Fix VM_FAULT_HWPOISON handling in do_exception()

There is no support for HWPOISON, MEMORY_FAILURE, or ARCH_HAS_COPY_MC on
s390. Therefore we do not expect to see VM_FAULT_HWPOISON in
do_exception().

However, since commit af19487f00f3 ("mm: make PTE_MARKER_SWAPIN_ERROR more
general"), it is possible to see VM_FAULT_HWPOISON in combination with
PTE_MARKER_POISONED, even on architectures that do not support HWPOISON
otherwise. In this case, we will end up on the BUG() in do_exception().

Fix this by treating VM_FAULT_HWPOISON the same as VM_FAULT_SIGBUS, similar
to x86 when MEMORY_FAILURE is not configured. Also print unexpected fault
flags, for easier debugging.

Note that VM_FAULT_HWPOISON_LARGE is not expected, because s390 cannot
support swap entries on other levels than PTE level.

The Linux kernel CVE team has assigned CVE-2024-41021 to this issue.

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

	Issue introduced in 6.6 with commit af19487f00f3 and fixed in 6.6.44 with commit 73a9260b7366
	Issue introduced in 6.6 with commit af19487f00f3 and fixed in 6.9.12 with commit 9e13767ccefd
	Issue introduced in 6.6 with commit af19487f00f3 and fixed in 6.10.2 with commit a3aefb871222
	Issue introduced in 6.6 with commit af19487f00f3 and fixed in 6.11 with commit df39038cd895

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-2024-41021
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/s390/mm/fault.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/73a9260b7366d2906ec011e100319359fe2277d0
	https://git.kernel.org/stable/c/9e13767ccefdc4f8aa92514b592b60f6b54882ff
	https://git.kernel.org/stable/c/a3aefb871222a9880602d1a44a558177b4143e3b
	https://git.kernel.org/stable/c/df39038cd89525d465c2c8827eb64116873f141a