---
id: CVE-2023-52761
title: 'riscv: VMAP_STACK overflow detection thread-safe'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  riscv: VMAP_STACK overflow detection thread-safe

  commit 31da94c25aea ("riscv: add VMAP_STACK overflow detection") added
  support for CONFIG_VMAP_STACK. If overflow is d…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 <
    fbf55cd7d342507e8b029fab5e36033d81823845
  - >-
    Linux >= 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 <
    1493baaf09e3c1899959c8a107cd1207e16d1788
  - >-
    Linux >= 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 <
    eff53aea3855f71992c043cebb1c00988c17ee20
  - >-
    Linux >= 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 <
    be97d0db5f44c0674480cb79ac6f5b0529b84c76
  - Linux 4.15
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2024-06-11T15:20:22.458093Z'
published: '2024-05-21'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T12:17:21.964Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2023-52761'
references:
  - url: 'https://git.kernel.org/stable/c/fbf55cd7d342507e8b029fab5e36033d81823845'
  - url: 'https://git.kernel.org/stable/c/1493baaf09e3c1899959c8a107cd1207e16d1788'
  - url: 'https://git.kernel.org/stable/c/eff53aea3855f71992c043cebb1c00988c17ee20'
  - url: 'https://git.kernel.org/stable/c/be97d0db5f44c0674480cb79ac6f5b0529b84c76'
tags:
  - cve.org
epss: 0.00267
epssPercentile: 0.18928
ingestedAt: '2026-11-03T11:43:15.783Z'
---

## Overview

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

riscv: VMAP_STACK overflow detection thread-safe

commit 31da94c25aea ("riscv: add VMAP_STACK overflow detection") added
support for CONFIG_VMAP_STACK. If overflow is detected, CPU switches to
`shadow_stack` temporarily before switching finally to per-cpu
`overflow_stack`.

If two CPUs/harts are racing and end up in over flowing kernel stack, one
or both will end up corrupting each other state because `shadow_stack` is
not per-cpu. This patch optimizes per-cpu overflow stack switch by
directly picking per-cpu `overflow_stack` and gets rid of `shadow_stack`.

Following are the changes in this patch

 - Defines an asm macro to obtain per-cpu symbols in destination
   register.
 - In entry.S, when overflow is detected, per-cpu overflow stack is
   located using per-cpu asm macro. Computing per-cpu symbol requires
   a temporary register. x31 is saved away into CSR_SCRATCH
   (CSR_SCRATCH is anyways zero since we're in kernel).

Please see Links for additional relevant disccussion and alternative
solution.

Tested by `echo EXHAUST_STACK > /sys/kernel/debug/provoke-crash/DIRECT`
Kernel crash log below

 Insufficient stack space to handle exception!/debug/provoke-crash/DIRECT
 Task stack:     [0xff20000010a98000..0xff20000010a9c000]
 Overflow stack: [0xff600001f7d98370..0xff600001f7d99370]
 CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34
 Hardware name: riscv-virtio,qemu (DT)
 epc : __memset+0x60/0xfc
  ra : recursive_loop+0x48/0xc6 [lkdtm]
 epc : ffffffff808de0e4 ra : ffffffff0163a752 sp : ff20000010a97e80
  gp : ffffffff815c0330 tp : ff600000820ea280 t0 : ff20000010a97e88
  t1 : 000000000000002e t2 : 3233206874706564 s0 : ff20000010a982b0
  s1 : 0000000000000012 a0 : ff20000010a97e88 a1 : 0000000000000000
  a2 : 0000000000000400 a3 : ff20000010a98288 a4 : 0000000000000000
  a5 : 0000000000000000 a6 : fffffffffffe43f0 a7 : 00007fffffffffff
  s2 : ff20000010a97e88 s3 : ffffffff01644680 s4 : ff20000010a9be90
  s5 : ff600000842ba6c0 s6 : 00aaaaaac29e42b0 s7 : 00fffffff0aa3684
  s8 : 00aaaaaac2978040 s9 : 0000000000000065 s10: 00ffffff8a7cad10
  s11: 00ffffff8a76a4e0 t3 : ffffffff815dbaf4 t4 : ffffffff815dbaf4
  t5 : ffffffff815dbab8 t6 : ff20000010a9bb48
 status: 0000000200000120 badaddr: ff20000010a97e88 cause: 000000000000000f
 Kernel panic - not syncing: Kernel stack overflow
 CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34
 Hardware name: riscv-virtio,qemu (DT)
 Call Trace:
 [<ffffffff80006754>] dump_backtrace+0x30/0x38
 [<ffffffff808de798>] show_stack+0x40/0x4c
 [<ffffffff808ea2a8>] dump_stack_lvl+0x44/0x5c
 [<ffffffff808ea2d8>] dump_stack+0x18/0x20
 [<ffffffff808dec06>] panic+0x126/0x2fe
 [<ffffffff800065ea>] walk_stackframe+0x0/0xf0
 [<ffffffff0163a752>] recursive_loop+0x48/0xc6 [lkdtm]
 SMP: stopping secondary CPUs
 ---[ end Kernel panic - not syncing: Kernel stack overflow ]---

## Affected

- `Linux >= 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 < fbf55cd7d342507e8b029fab5e36033d81823845`
- `Linux >= 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 < 1493baaf09e3c1899959c8a107cd1207e16d1788`
- `Linux >= 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 < eff53aea3855f71992c043cebb1c00988c17ee20`
- `Linux >= 76d2a0493a17d4c8ecc781366850c3c4f8e1a446 < be97d0db5f44c0674480cb79ac6f5b0529b84c76`
- `Linux 4.15`

## Remediation

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