---
id: CVE-2023-53121
title: 'tcp: tcp_make_synack() can be called from process context'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  tcp: tcp_make_synack() can be called from process context

  tcp_rtx_synack() now could be called in process context as explained in
  0a375c822497 ("tcp: tcp_rtx_synack() …
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 <
    d493d4fe88195a144d6a277a90062a7534ed2192
  - >-
    Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 <
    e23ca307745be3df7fe9762f3e2a7e311a57852e
  - >-
    Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 <
    442aa78ed70188b21ccd8669738448702c0a3281
  - >-
    Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 <
    77ad58bca0119e8cc3e0e9d91a3f22caa66e4dfa
  - >-
    Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 <
    ad07290d63ff6689f50565b02f5b6f34ec15a5ca
  - >-
    Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 <
    9180aa4622a720b433e842b4d3aa34d73eec577a
  - >-
    Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 <
    7613cde8c0c1f02a7ec2e1d536c01b65b135fc1c
  - >-
    Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 <
    bced3f7db95ff2e6ca29dc4d1c9751ab5e736a09
  - Linux 3.7
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T20:18:11.326915Z'
published: '2025-05-02'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:21:02.884Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2023-53121'
references:
  - url: 'https://git.kernel.org/stable/c/d493d4fe88195a144d6a277a90062a7534ed2192'
  - url: 'https://git.kernel.org/stable/c/e23ca307745be3df7fe9762f3e2a7e311a57852e'
  - url: 'https://git.kernel.org/stable/c/442aa78ed70188b21ccd8669738448702c0a3281'
  - url: 'https://git.kernel.org/stable/c/77ad58bca0119e8cc3e0e9d91a3f22caa66e4dfa'
  - url: 'https://git.kernel.org/stable/c/ad07290d63ff6689f50565b02f5b6f34ec15a5ca'
  - url: 'https://git.kernel.org/stable/c/9180aa4622a720b433e842b4d3aa34d73eec577a'
  - url: 'https://git.kernel.org/stable/c/7613cde8c0c1f02a7ec2e1d536c01b65b135fc1c'
  - url: 'https://git.kernel.org/stable/c/bced3f7db95ff2e6ca29dc4d1c9751ab5e736a09'
tags:
  - cve.org
epss: 0.00189
epssPercentile: 0.08523
ingestedAt: '2026-11-05T22:38:31.774Z'
---

## Overview

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

tcp: tcp_make_synack() can be called from process context

tcp_rtx_synack() now could be called in process context as explained in
0a375c822497 ("tcp: tcp_rtx_synack() can be called from process
context").

tcp_rtx_synack() might call tcp_make_synack(), which will touch per-CPU
variables with preemption enabled. This causes the following BUG:

    BUG: using __this_cpu_add() in preemptible [00000000] code: ThriftIO1/5464
    caller is tcp_make_synack+0x841/0xac0
    Call Trace:
     <TASK>
     dump_stack_lvl+0x10d/0x1a0
     check_preemption_disabled+0x104/0x110
     tcp_make_synack+0x841/0xac0
     tcp_v6_send_synack+0x5c/0x450
     tcp_rtx_synack+0xeb/0x1f0
     inet_rtx_syn_ack+0x34/0x60
     tcp_check_req+0x3af/0x9e0
     tcp_rcv_state_process+0x59b/0x2030
     tcp_v6_do_rcv+0x5f5/0x700
     release_sock+0x3a/0xf0
     tcp_sendmsg+0x33/0x40
     ____sys_sendmsg+0x2f2/0x490
     __sys_sendmsg+0x184/0x230
     do_syscall_64+0x3d/0x90

Avoid calling __TCP_INC_STATS() with will touch per-cpu variables. Use
TCP_INC_STATS() which is safe to be called from context switch.

## Affected

- `Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 < d493d4fe88195a144d6a277a90062a7534ed2192`
- `Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 < e23ca307745be3df7fe9762f3e2a7e311a57852e`
- `Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 < 442aa78ed70188b21ccd8669738448702c0a3281`
- `Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 < 77ad58bca0119e8cc3e0e9d91a3f22caa66e4dfa`
- `Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 < ad07290d63ff6689f50565b02f5b6f34ec15a5ca`
- `Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 < 9180aa4622a720b433e842b4d3aa34d73eec577a`
- `Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 < 7613cde8c0c1f02a7ec2e1d536c01b65b135fc1c`
- `Linux >= 8336886f786fdacbc19b719c1f7ea91eb70706d4 < bced3f7db95ff2e6ca29dc4d1c9751ab5e736a09`
- `Linux 3.7`

## Remediation

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