# CVE-2023-54116: drm/fbdev-generic: prohibit potential out-of-bounds access

> A local attacker can trigger an out-of-bounds write in the Linux kernel DRM subsystem, causing a system crash or hang.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Dec 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2023-54116, DEBIAN-CVE-2023-54116, GHSA-99xh-3c2q-rwgv, UBUNTU-CVE-2023-54116

## What is CVE-2023-54116?

CVE-2023-54116 is a high-severity memory corruption vulnerability in Linux, published on 24 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

drm/fbdev-generic: prohibit potential out-of-bounds access

The fbdev test of IGT may write after EOF, which lead to out-of-bound
access for drm drivers with fbdev-generic. For example, run fbdev test
on a x86+ast2400 platform, with 1680x1050 resolution, will cause the
linux kernel hang with the following call trace:

  Oops: 0000 [#1] PREEMPT SMP PTI
  [IGT] fbdev: starting subtest eof
  Workqueue: events drm_fb_helper_damage_work [drm_kms_helper]
  [IGT] fbdev: starting subtest nullptr

  RIP: 0010:memcpy_erms+0xa/0x20
  RSP: 0018:ffffa17d40167d98 EFLAGS: 00010246
  RAX: ffffa17d4eb7fa80 RBX: ffffa17d40e0aa80 RCX: 00000000000014c0
  RDX: 0000000000001a40 RSI: ffffa17d40e0b000 RDI: ffffa17d4eb80000
  RBP: ffffa17d40167e20 R08: 0000000000000000 R09: ffff89522ecff8c0
  R10: ffffa17d4e4c5000 R11: 0000000000000000 R12: ffffa17d4eb7fa80
  R13: 0000000000001a40 R14: 000000000000041a R15: ffffa17d40167e30
  FS:  0000000000000000(0000) GS:ffff895257380000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: ffffa17d40e0b000 CR3: 00000001eaeca006 CR4: 00000000001706e0
  Call Trace:
   <TASK>
   ? drm_fbdev_generic_helper_fb_dirty+0x207/0x330 [drm_kms_helper]
   drm_fb_helper_damage_work+0x8f/0x170 [drm_kms_helper]
   process_one_work+0x21f/0x430
   worker_thread+0x4e/0x3c0
   ? __pfx_worker_thread+0x10/0x10
   kthread+0xf4/0x120
   ? __pfx_kthread+0x10/0x10
   ret_from_fork+0x2c/0x50
   </TASK>
  CR2: ffffa17d40e0b000
  ---[ end trace 0000000000000000 ]---

The is because damage rectangles computed by
drm_fb_helper_memory_range_to_clip() function is not guaranteed to be
bound in the screen's active display area. Possible reasons are:

1) Buffers are allocated in the granularity of page size, for mmap system
   call support. The shadow screen buffer consumed by fbdev emulation may
   also choosed be page size aligned.

2) The DIV_ROUND_UP() used in drm_fb_helper_memory_range_to_clip()
   will introduce off-by-one error.

For example, on a 16KB page size system, in order to store a 1920x1080
XRGB framebuffer, we need allocate 507 pages. Unfortunately, the size
1920*1080*4 can not be divided exactly by 16KB.

 1920 * 1080 * 4 = 8294400 bytes
 506 * 16 * 1024 = 8290304 bytes
 507 * 16 * 1024 = 8306688 bytes

 line_length = 1920*4 = 7680 bytes

 507 * 16 * 1024 / 7680 = 1081.6

 off / line_length = 507 * 16 * 1024 / 7680 = 1081
 DIV_ROUND_UP(507 * 16 * 1024, 7680) will yeild 1082

memcpy_toio() typically issue the copy line by line, when copy the last
line, out-of-bound access will be happen. Because:

 1082 * line_length = 1082 * 7680 = 8309760, and 8309760 > 8306688

Note that userspace may still write to the invisiable area if a larger
buffer than width x stride is exposed. But it is not a big issue as
long as there still have memory resolve the access if not drafting so
far.

 - Also limit the y1 (Daniel)
 - keep fix patch it to minimal (Daniel)
 - screen_size is page size aligned because of it need mmap (Thomas)
 - Adding fixes tag (Thomas)

## Which versions are affected by CVE-2023-54116?


## How do I fix CVE-2023-54116?

Apply the vendor's patch.

## Is CVE-2023-54116 being exploited?

There is no known exploitation of CVE-2023-54116 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-54116 and fix it if it is affected.

What it is: CVE-2023-54116 is a high-severity memory corruption vulnerability in Linux, published on 24 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-54116 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-54116/ (Markdown: https://insights.sbomify.com/CVE-2023-54116/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-54116
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-54116
- OSV: https://osv.dev/vulnerability/CVE-2023-54116

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-54116/
Summaries are generated and may contain mistakes; the official description above is the record.