# CVE-2026-90218: RDMA/cma: Fix WARNING in res_to_rt

> A null pointer dereference in the Linux kernel RDMA subsystem allows local attackers to trigger a kernel warning and potential denial of service.

- **Severity:** Not scored
- **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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-102585, BELL-CVE-2026-90218, DEBIAN-CVE-2026-90218, GHSA-674r-g85v-jff6, UBUNTU-CVE-2026-90218

## What is CVE-2026-90218?

CVE-2026-90218 is a 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:

RDMA/cma: Fix WARNING in res_to_rt

syzbot reported a WARN_ON(!res->dev) in res_to_rt() triggered via
addr_handler() during asynchronous address resolution:

"
WARNING: drivers/infiniband/core/restrack.c:138 at res_to_rt+0x1c4/0x230
CPU#1: kworker/u8:4/59
Modules linked in:
CPU: 1 UID: 0 PID: 59 Comm: kworker/u8:4 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Compute Engine, BIOS Google 07/24/2026
Workqueue: ib_addr process_one_req
RIP: 0010:res_to_rt+0x1c4/0x230 drivers/infiniband/core/restrack.c:138
RSP: 0018:ffffc9000201f850 EFLAGS: 00010293
RAX: ffffffff88d00ce5 RBX: ffff88807f0fd4f8 RCX: ffff88801e6e0000
RDX: 0000000000000000 RSI: ffffffff8fd996f0 RDI: 0000000000000003
RBP: 0000000000000000 R08: ffff88801e6e0000 R09: 000000000000000a
R10: 0000000000000009 R11: 0000000000000000 R12: dffffc0000000000
R13: 1ffff1100fe1fa9f R14: 0000000000000000 R15: 0000000000000003
FS:  0000000000000000(0000) GS:ffff888125012000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00001d559c3d2000 CR3: 0000000077c4c000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 rdma_restrack_add+0x5a/0x8a0 drivers/infiniband/core/restrack.c:236
 addr_handler+0x41a/0x5a0 drivers/infiniband/core/cma.c:3534
 process_one_req+0x2eb/0x540 drivers/infiniband/core/addr.c:624
 process_one_work kernel/workqueue.c:3375 [inline]
 process_scheduled_works+0xc4e/0x1630 kernel/workqueue.c:3458
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3539
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
"

In addr_handler(), cma_acquire_dev_by_src_ip() is called to populate
id_priv->cma_dev and bind the associated ib_device to id_priv->id.device.
If cma_acquire_dev_by_src_ip() returns an error (non-zero status), the ID
remains unassociated with any RDMA device.

Previously, rdma_restrack_add(&id_priv->res) was invoked unconditionally
even when cma_acquire_dev_by_src_ip() failed, passing a resource with a
NULL dev pointer and triggering the WARN_ON assertion in res_to_rt().

Fix this by only adding the resource to restrack when acquiring the device
succeeds.

## Which versions are affected by CVE-2026-90218?


## How do I fix CVE-2026-90218?

Apply the vendor's patch.

## Is CVE-2026-90218 being exploited?

There is no known exploitation of CVE-2026-90218 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90218 and fix it if it is affected.

What it is: CVE-2026-90218 is a 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-2026-90218 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-2026-90218/ (Markdown: https://insights.sbomify.com/CVE-2026-90218/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90218
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90218
- OSV: https://osv.dev/vulnerability/CVE-2026-90218

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90218/
Summaries are generated and may contain mistakes; the official description above is the record.