# CVE-2026-93168: dmaengine: xilinx_dma: Fix CPU stall in xilinx_dma_poll_timeout

> A flaw in the Xilinx DMA driver causes CPU stalls during timeout conditions, leading to denial of service for local attackers.

- **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:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-102399, BELL-CVE-2026-93168, DEBIAN-CVE-2026-93168, GHSA-r3mw-x3xp-fjpr, UBUNTU-CVE-2026-93168

## What is CVE-2026-93168?

CVE-2026-93168 is a denial of service vulnerability in Linux, published on 17 Sep 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:

dmaengine: xilinx_dma: Fix CPU stall in xilinx_dma_poll_timeout

Currently when calling xilinx_dma_poll_timeout with delay_us=0 and a
condition that is never fulfilled, the CPU busy-waits for prolonged time
and the timeout triggers only with a massive delay causing a CPU stall.

This happens due to a huge underestimation of wall clock time in
poll_timeout_us_atomic. Commit 7349a69cf312 ("iopoll: Do not use
timekeeping in read_poll_timeout_atomic()") changed the behavior to no
longer use ktime_get at the expense of underestimation of wall clock
time which appears to be very large for delay_us=0. Instead of timing
out after approximately XILINX_DMA_LOOP_COUNT microseconds, the timeout
takes XILINX_DMA_LOOP_COUNT * 1000 * (time that the overhead of the for
loop in poll_timeout_us_atomic takes) which is in the range of several
minutes for XILINX_DMA_LOOP_COUNT=1000000. Fix this by using a non-zero
value for delay_us. Use delay_us=10 to keep the delay in the hot path of
starting DMA transfers minimal but still avoid CPU stalls in case of
unexpected hardware failures.

One-off measurement with delay_us=0 causes the cpu to busy wait around 7
minutes in the timeout case. After applying this patch with delay_us=10
the measured timeout was 1053428 microseconds which is roughly
equivalent to the expected 1000000 microseconds specified in
XILINX_DMA_LOOP_COUNT.

Add a constant XILINX_DMA_POLL_DELAY_US for delay_us value.

## Which versions are affected by CVE-2026-93168?


## How do I fix CVE-2026-93168?

Apply the vendor's patch.

## Is CVE-2026-93168 being exploited?

There is no known exploitation of CVE-2026-93168 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93168 and fix it if it is affected.

What it is: CVE-2026-93168 is a denial of service vulnerability in Linux, published on 17 Sep 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-2026-93168 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-2026-93168/ (Markdown: https://insights.sbomify.com/CVE-2026-93168/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93168
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93168
- OSV: https://osv.dev/vulnerability/CVE-2026-93168

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93168/
Summaries are generated and may contain mistakes; the official description above is the record.