# CVE-2026-68436: drm/amd/display: use kvzalloc to allocate struct dc

> A kernel bug causes AMD GPU display initialization to fail if the driver structure exceeds memory limits, resulting in a denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2026-68436, DEBIAN-CVE-2026-68436, GHSA-7q8m-jhfw-frrf, UBUNTU-CVE-2026-68436

## What is CVE-2026-68436?

CVE-2026-68436 is a denial of service vulnerability in Linux, published on 12 Aug 2026. 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/amd/display: use kvzalloc to allocate struct dc

struct dc has grown large over time (most of it the two inlined
dc_scratch_space copies) and now sits close to the page allocator's 4 MiB
contiguous allocation limit. Its actual size is not fixed by the source
alone, it also depends on the compiler and the .config, so it can easily
cross 4 MiB, e.g. with a newer GCC or a config change.

dc_create() allocates it with kzalloc(). Once struct dc exceeds 4 MiB the
request is rounded up to order 11 (8 MiB), which is above MAX_PAGE_ORDER,
so the page allocator warns and returns NULL. dc_create() then fails, DM
init fails and amdgpu probe aborts with -EINVAL:

  WARNING: mm/page_alloc.c:5197 at __alloc_frozen_pages_noprof+0x2f9/0x380
   dc_create+0x38/0x660 [amdgpu]
   amdgpu_dm_init+0x2d9/0x510 [amdgpu]
   dm_hw_init+0x1b/0x90 [amdgpu]
   amdgpu_device_init.cold+0x150d/0x1e13 [amdgpu]
   amdgpu_driver_load_kms+0x19/0x80 [amdgpu]
   amdgpu_pci_probe+0x1e2/0x4c0 [amdgpu]

dc_create() then returns NULL and DM init fails, which aborts the whole
GPU init and makes amdgpu probe fail with -EINVAL ("hw_init of IP block
<dm> failed -22"), leaving the display unusable. The subsequent
amdgpu_irq_put() warnings during teardown are just fallout of unwinding
a half-initialized device.

struct dc is a software-only bookkeeping structure that is never handed
to hardware DMA and is only ever kept as an opaque pointer, so it does
not require physically contiguous memory. Allocate it with kvzalloc()
(and free it with kvfree()) so that the allocator can fall back to
vmalloc() when a contiguous allocation of that size is not available,
which also avoids the MAX_PAGE_ORDER warning entirely.

v2:
 - Rebase to amd-staging-drm-next.

(cherry picked from commit 991e0516a8072f2292681c6ae98a924ab0e32575)

## Which versions are affected by CVE-2026-68436?


## How do I fix CVE-2026-68436?

Apply the vendor's patch.

## Is CVE-2026-68436 being exploited?

There is no known exploitation of CVE-2026-68436 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68436 and fix it if it is affected.

What it is: CVE-2026-68436 is a denial of service vulnerability in Linux, published on 12 Aug 2026. 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-2026-68436 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-2026-68436/ (Markdown: https://insights.sbomify.com/CVE-2026-68436/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68436
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68436
- OSV: https://osv.dev/vulnerability/CVE-2026-68436

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68436/
Summaries are generated and may contain mistakes; the official description above is the record.