# CVE-2021-47139: net: hns3: put off calling register_netdev() until client initialize complete

> A race condition in the hns3 network driver allows local users to trigger a kernel bug and crash the system by changing channel parameters during initialization.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 25 Mar 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47139, GHSA-6cwm-qhmw-g438, UBUNTU-CVE-2021-47139

## What is CVE-2021-47139?

CVE-2021-47139 is a medium-severity vulnerability in Linux kernel, published on 25 Mar 2024. 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:

net: hns3: put off calling register_netdev() until client initialize complete

Currently, the netdevice is registered before client initializing
complete. So there is a timewindow between netdevice available
and usable. In this case, if user try to change the channel number
or ring param, it may cause the hns3_set_rx_cpu_rmap() being called
twice, and report bug.

[47199.416502] hns3 0000:35:00.0 eth1: set channels: tqp_num=1, rxfh=0
[47199.430340] hns3 0000:35:00.0 eth1: already uninitialized
[47199.438554] hns3 0000:35:00.0: rss changes from 4 to 1
[47199.511854] hns3 0000:35:00.0: Channels changed, rss_size from 4 to 1, tqps from 4 to 1
[47200.163524] ------------[ cut here ]------------
[47200.171674] kernel BUG at lib/cpu_rmap.c:142!
[47200.177847] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[47200.185259] Modules linked in: hclge(+) hns3(-) hns3_cae(O) hns_roce_hw_v2 hnae3 vfio_iommu_type1 vfio_pci vfio_virqfd vfio pv680_mii(O) [last unloaded: hclge]
[47200.205912] CPU: 1 PID: 8260 Comm: ethtool Tainted: G           O      5.11.0-rc3+ #1
[47200.215601] Hardware name:  , xxxxxx 02/04/2021
[47200.223052] pstate: 60400009 (nZCv daif +PAN -UAO -TCO BTYPE=--)
[47200.230188] pc : cpu_rmap_add+0x38/0x40
[47200.237472] lr : irq_cpu_rmap_add+0x84/0x140
[47200.243291] sp : ffff800010e93a30
[47200.247295] x29: ffff800010e93a30 x28: ffff082100584880
[47200.254155] x27: 0000000000000000 x26: 0000000000000000
[47200.260712] x25: 0000000000000000 x24: 0000000000000004
[47200.267241] x23: ffff08209ba03000 x22: ffff08209ba038c0
[47200.273789] x21: 000000000000003f x20: ffff0820e2bc1680
[47200.280400] x19: ffff0820c970ec80 x18: 00000000000000c0
[47200.286944] x17: 0000000000000000 x16: ffffb43debe4a0d0
[47200.293456] x15: fffffc2082990600 x14: dead000000000122
[47200.300059] x13: ffffffffffffffff x12: 000000000000003e
[47200.306606] x11: ffff0820815b8080 x10: ffff53e411988000
[47200.313171] x9 : 0000000000000000 x8 : ffff0820e2bc1700
[47200.319682] x7 : 0000000000000000 x6 : 000000000000003f
[47200.326170] x5 : 0000000000000040 x4 : ffff800010e93a20
[47200.332656] x3 : 0000000000000004 x2 : ffff0820c970ec80
[47200.339168] x1 : ffff0820e2bc1680 x0 : 0000000000000004
[47200.346058] Call trace:
[47200.349324]  cpu_rmap_add+0x38/0x40
[47200.354300]  hns3_set_rx_cpu_rmap+0x6c/0xe0 [hns3]
[47200.362294]  hns3_reset_notify_init_enet+0x1cc/0x340 [hns3]
[47200.370049]  hns3_change_channels+0x40/0xb0 [hns3]
[47200.376770]  hns3_set_channels+0x12c/0x2a0 [hns3]
[47200.383353]  ethtool_set_channels+0x140/0x250
[47200.389772]  dev_ethtool+0x714/0x23d0
[47200.394440]  dev_ioctl+0x4cc/0x640
[47200.399277]  sock_do_ioctl+0x100/0x2a0
[47200.404574]  sock_ioctl+0x28c/0x470
[47200.409079]  __arm64_sys_ioctl+0xb4/0x100
[47200.415217]  el0_svc_common.constprop.0+0x84/0x210
[47200.422088]  do_el0_svc+0x28/0x34
[47200.426387]  el0_svc+0x28/0x70
[47200.431308]  el0_sync_handler+0x1a4/0x1b0
[47200.436477]  el0_sync+0x174/0x180
[47200.441562] Code: 11000405 79000c45 f8247861 d65f03c0 (d4210000)
[47200.448869] ---[ end trace a01efe4ce42e5f34 ]---

The process is like below:
excuting hns3_client_init
|
register_netdev()
|                           hns3_set_channels()
|                           |
hns3_set_rx_cpu_rmap()      hns3_reset_notify_uninit_enet()
|                               |
|                            quit without calling function
|                            hns3_free_rx_cpu_rmap for flag
|                            HNS3_NIC_STATE_INITED is unset.
|                           |
|                           hns3_reset_notify_init_enet()
|                               |
set HNS3_NIC_STATE_INITED    call hns3_set_rx_cpu_rmap()-- crash

Fix it by calling register_netdev() at the end of function
hns3_client_init().

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2021-47139?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47139?

Apply the vendor's patch.

## Is CVE-2021-47139 being exploited?

There is no known exploitation of CVE-2021-47139 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47139 and fix it if it is affected.

What it is: CVE-2021-47139 is a medium-severity vulnerability in Linux kernel, published on 25 Mar 2024. 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-2021-47139 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2021-47139/ (Markdown: https://insights.sbomify.com/CVE-2021-47139/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47139
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47139
- OSV: https://osv.dev/vulnerability/CVE-2021-47139

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47139/
Summaries are generated and may contain mistakes; the official description above is the record.