linux-cve-announce - CVE-2023-53702: s390/crypto: use vector instructions only if available for ChaCha20

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Message-ID: <2025102211-CVE-2023-53702-a6b6@gregkh>
Date: Wed, 22 Oct 2025 15:24:41 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53702: s390/crypto: use vector instructions only if available for ChaCha20

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

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

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

s390/crypto: use vector instructions only if available for ChaCha20

Commit 349d03ffd5f6 ("crypto: s390 - add crypto library interface for
ChaCha20") added a library interface to the s390 specific ChaCha20
implementation. However no check was added to verify if the required
facilities are installed before branching into the assembler code.

If compiled into the kernel, this will lead to the following crash,
if vector instructions are not available:

data exception: 0007 ilc:3 [#1] SMP
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.3.0-rc7+ #11
Hardware name: IBM 3931 A01 704 (KVM/Linux)
Krnl PSW : 0704e00180000000 000000001857277a (chacha20_vx+0x32/0x818)
           R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3
Krnl GPRS: 0000037f0000000a ffffffffffffff60 000000008184b000 0000000019f5c8e6
           0000000000000109 0000037fffb13c58 0000037fffb13c78 0000000019bb1780
           0000037fffb13c58 0000000019f5c8e6 000000008184b000 0000000000000109
           00000000802d8000 0000000000000109 0000000018571ebc 0000037fffb13718
Krnl Code: 000000001857276a: c07000b1f80b        larl    %r7,0000000019bb1780
           0000000018572770: a708000a            lhi     %r0,10
          #0000000018572774: e78950000c36        vlm     %v24,%v25,0(%r5),0
          >000000001857277a: e7a060000806        vl      %v26,0(%r6),0
           0000000018572780: e7bf70004c36        vlm     %v27,%v31,0(%r7),4
           0000000018572786: e70b00000456        vlr     %v0,%v27
           000000001857278c: e71800000456        vlr     %v1,%v24
           0000000018572792: e74b00000456        vlr     %v4,%v27
Call Trace:
 [<000000001857277a>] chacha20_vx+0x32/0x818
Last Breaking-Event-Address:
 [<0000000018571eb6>] chacha20_crypt_s390.constprop.0+0x6e/0xd8
---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b

Fix this by adding a missing MACHINE_HAS_VX check.

[agordeev@...ux.ibm.com: remove duplicates in commit message]

The Linux kernel CVE team has assigned CVE-2023-53702 to this issue.


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

	Issue introduced in 5.19 with commit 349d03ffd5f62c298fd667ffa397c3fdc5c6194b and fixed in 6.1.30 with commit 25e8d30507aa2f251152df1af7809e85b5538f4a
	Issue introduced in 5.19 with commit 349d03ffd5f62c298fd667ffa397c3fdc5c6194b and fixed in 6.3.4 with commit debb7797bba0caffdbdadc3e7968bb2c414f50da
	Issue introduced in 5.19 with commit 349d03ffd5f62c298fd667ffa397c3fdc5c6194b and fixed in 6.4 with commit 8703dd6b238da0ec6c276e53836f8200983d3d9b

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-2023-53702
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/crypto/chacha-glue.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/25e8d30507aa2f251152df1af7809e85b5538f4a
	https://git.kernel.org/stable/c/debb7797bba0caffdbdadc3e7968bb2c414f50da
	https://git.kernel.org/stable/c/8703dd6b238da0ec6c276e53836f8200983d3d9b