---
id: CVE-2026-93167
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  csky: Fix a4/a5 restoration in syscall trace path

  The syscall trace path reloads syscall arguments from pt_regs before
  calling the syscall handler
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  csky: Fix a4/a5 restoration in syscall trace path

  The syscall trace path reloads syscall arguments from pt_regs before
  calling the syscall handler. On C-SKY ABIv2, the…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= e0bbb53843b5fdfe464b099217e3b9d97e8a75d7 <
    e9ae8e86eed68bea5d2670eadf61938a43bd2263
  - >-
    Linux >= e0bbb53843b5fdfe464b099217e3b9d97e8a75d7 <
    64e3ec7a71d3b715e2567f19f64207f04999bb0c
  - >-
    Linux >= e0bbb53843b5fdfe464b099217e3b9d97e8a75d7 <
    863fa63fd1491f201ac819f805a8db98d2a32c3d
  - >-
    Linux >= e0bbb53843b5fdfe464b099217e3b9d97e8a75d7 <
    e71a3dc5b8d2ea4d9cfbdb135d6b7777de84212e
  - >-
    Linux >= e0bbb53843b5fdfe464b099217e3b9d97e8a75d7 <
    31c81b376e5f058c7f2c94f69719cf7caec2fc3f
  - >-
    Linux >= e0bbb53843b5fdfe464b099217e3b9d97e8a75d7 <
    a776afa89424570bfa637ebf812ca281a5732904
  - >-
    Linux >= e0bbb53843b5fdfe464b099217e3b9d97e8a75d7 <
    343aa5275484d627c921a42e8e115cae366be5de
  - >-
    Linux >= e0bbb53843b5fdfe464b099217e3b9d97e8a75d7 <
    abb81e5ce7d995baa41556b8125fa59e28ba3be8
  - Linux 108681048cf728a8570e036c34ebd7daa43133b4
  - Linux 3a5837c692918c229baf63fe7950965d27c48ac2
  - Linux >= 5.4.47 < 5.5
  - Linux >= 5.6.19 < 5.7
  - Linux 5.7
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:18:12.243'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93167'
references:
  - url: 'https://git.kernel.org/stable/c/31c81b376e5f058c7f2c94f69719cf7caec2fc3f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/343aa5275484d627c921a42e8e115cae366be5de'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/64e3ec7a71d3b715e2567f19f64207f04999bb0c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/863fa63fd1491f201ac819f805a8db98d2a32c3d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a776afa89424570bfa637ebf812ca281a5732904'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/abb81e5ce7d995baa41556b8125fa59e28ba3be8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e71a3dc5b8d2ea4d9cfbdb135d6b7777de84212e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e9ae8e86eed68bea5d2670eadf61938a43bd2263'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.732Z'
epss: 0.00211
epssPercentile: 0.1159
---

## Overview

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

csky: Fix a4/a5 restoration in syscall trace path

The syscall trace path reloads syscall arguments from pt_regs before
calling the syscall handler. On C-SKY ABIv2, the 5th and 6th syscall
arguments are prepared as stack arguments before invoking syscallid.

The current code adjusts sp before loading LSAVE_A4 and LSAVE_A5. Since
those offsets are relative to the original pt_regs base, loading them
after changing sp fetches the wrong slots. As a result, traced syscalls
that use the 5th or 6th argument may receive corrupted arguments.

This is visible with mmap2(), which takes six arguments. A small
PTRACE_SYSCALL reproducer opens a file and maps one page with:

  mmap(NULL, 4096, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0)

Before the fix, the traced child fails the mmap and exits with 12.
After the fix, the mapping succeeds and the child exits with 0.

Fix the trace path by loading a4/a5 from pt_regs before changing sp.

Tested on: ck860f, linux-4.19.15, C-SKY abiv2

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.