---
id: CVE-2023-52438
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  binder: fix use-after-free in shinker's callback

  The mmap read lock is used during the shrinker's callback, which means
  that using alloc->vma pointer isn't safe as it …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  binder: fix use-after-free in shinker's callback

  The mmap read lock is used during the shrinker's callback, which means
  that using alloc->vma pointer isn't safe as it …
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'
cwe:
  - CWE-416
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 4.20.0, < 5.4.268'
  - 'linux_kernel >= 5.5.0, < 5.10.209'
  - 'linux_kernel >= 5.11.0, < 5.15.148'
  - 'linux_kernel >= 5.16.0, < 6.1.74'
  - 'linux_kernel >= 6.2.0, < 6.6.13'
  - 'linux_kernel >= 6.7.0, < 6.7.1'
patched:
  - linux_kernel 6.7.1
published: '2024-02-20'
updated: '2026-08-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-52438'
references:
  - url: 'https://git.kernel.org/stable/c/3f489c2067c5824528212b0fc18b28d51332d906'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8ad4d580e8aff8de2a4d57c5930fcc29f1ffd4a6'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9fa04c93f24138747807fe75b5591bb680098f56'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a49087ab93508b60d9b8add91707a22dda832869'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a53e15e592b4dcc91c3a3b8514e484a0bdbc53a3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c8c1158ffb007197f31f9d9170cf13e4f34cbb5c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e074686e993ff1be5f21b085a3b1b4275ccd5727'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3f489c2067c5824528212b0fc18b28d51332d906'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/8ad4d580e8aff8de2a4d57c5930fcc29f1ffd4a6'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/9fa04c93f24138747807fe75b5591bb680098f56'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/a49087ab93508b60d9b8add91707a22dda832869'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/a53e15e592b4dcc91c3a3b8514e484a0bdbc53a3'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/c8c1158ffb007197f31f9d9170cf13e4f34cbb5c'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/e074686e993ff1be5f21b085a3b1b4275ccd5727'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2024/06/msg00016.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00295
epssPercentile: 0.19758
ingestedAt: '2026-08-04T10:39:37.400Z'
---

## Overview

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

binder: fix use-after-free in shinker's callback

The mmap read lock is used during the shrinker's callback, which means
that using alloc->vma pointer isn't safe as it can race with munmap().
As of commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in
munmap") the mmap lock is downgraded after the vma has been isolated.

I was able to reproduce this issue by manually adding some delays and
triggering page reclaiming through the shrinker's debug sysfs. The
following KASAN report confirms the UAF:

  ==================================================================
  BUG: KASAN: slab-use-after-free in zap_page_range_single+0x470/0x4b8
  Read of size 8 at addr ffff356ed50e50f0 by task bash/478

  CPU: 1 PID: 478 Comm: bash Not tainted 6.6.0-rc5-00055-g1c8b86a3799f-dirty #70
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   zap_page_range_single+0x470/0x4b8
   binder_alloc_free_page+0x608/0xadc
   __list_lru_walk_one+0x130/0x3b0
   list_lru_walk_node+0xc4/0x22c
   binder_shrink_scan+0x108/0x1dc
   shrinker_debugfs_scan_write+0x2b4/0x500
   full_proxy_write+0xd4/0x140
   vfs_write+0x1ac/0x758
   ksys_write+0xf0/0x1dc
   __arm64_sys_write+0x6c/0x9c

  Allocated by task 492:
   kmem_cache_alloc+0x130/0x368
   vm_area_alloc+0x2c/0x190
   mmap_region+0x258/0x18bc
   do_mmap+0x694/0xa60
   vm_mmap_pgoff+0x170/0x29c
   ksys_mmap_pgoff+0x290/0x3a0
   __arm64_sys_mmap+0xcc/0x144

  Freed by task 491:
   kmem_cache_free+0x17c/0x3c8
   vm_area_free_rcu_cb+0x74/0x98
   rcu_core+0xa38/0x26d4
   rcu_core_si+0x10/0x1c
   __do_softirq+0x2fc/0xd24

  Last potentially related work creation:
   __call_rcu_common.constprop.0+0x6c/0xba0
   call_rcu+0x10/0x1c
   vm_area_free+0x18/0x24
   remove_vma+0xe4/0x118
   do_vmi_align_munmap.isra.0+0x718/0xb5c
   do_vmi_munmap+0xdc/0x1fc
   __vm_munmap+0x10c/0x278
   __arm64_sys_munmap+0x58/0x7c

Fix this issue by performing instead a vma_lookup() which will fail to
find the vma that was isolated before the mmap lock downgrade. Note that
this option has better performance than upgrading to a mmap write lock
which would increase contention. Plus, mmap_write_trylock() has been
recently removed anyway.

## Affected

- `linux_kernel >= 4.20.0, < 5.4.268`
- `linux_kernel >= 5.5.0, < 5.10.209`
- `linux_kernel >= 5.11.0, < 5.15.148`
- `linux_kernel >= 5.16.0, < 6.1.74`
- `linux_kernel >= 6.2.0, < 6.6.13`
- `linux_kernel >= 6.7.0, < 6.7.1`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.7.1`