# CVE-2021-47197: net/mlx5e: nullify cq->dbg pointer in mlx5_debug_cq_remove()

> A null pointer dereference in the Linux kernel mlx5 driver allows local attackers to cause a system crash via double-free logic errors.

- **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:** 10 Apr 2024
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2021-47197, GHSA-qrq5-v2rp-9c3f, UBUNTU-CVE-2021-47197

## What is CVE-2021-47197?

CVE-2021-47197 is a high-severity vulnerability in Linux kernel, published on 10 Apr 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/mlx5e: nullify cq->dbg pointer in mlx5_debug_cq_remove()

Prior to this patch in case mlx5_core_destroy_cq() failed it proceeds
to rest of destroy operations. mlx5_core_destroy_cq() could be called again
by user and cause additional call of mlx5_debug_cq_remove().
cq->dbg was not nullify in previous call and cause the crash.

Fix it by nullify cq->dbg pointer after removal.

Also proceed to destroy operations only if FW return 0
for MLX5_CMD_OP_DESTROY_CQ command.

general protection fault, probably for non-canonical address 0x2000300004058: 0000 [#1] SMP PTI
CPU: 5 PID: 1228 Comm: python Not tainted 5.15.0-rc5_for_upstream_min_debug_2021_10_14_11_06 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
RIP: 0010:lockref_get+0x1/0x60
Code: 5d e9 53 ff ff ff 48 8d 7f 70 e8 0a 2e 48 00 c7 85 d0 00 00 00 02
00 00 00 c6 45 70 00 fb 5d c3 c3 cc cc cc cc cc cc cc cc 53 <48> 8b 17
48 89 fb 85 d2 75 3d 48 89 d0 bf 64 00 00 00 48 89 c1 48
RSP: 0018:ffff888137dd7a38 EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffff888107d5f458 RCX: 00000000fffffffe
RDX: 000000000002c2b0 RSI: ffffffff8155e2e0 RDI: 0002000300004058
RBP: ffff888137dd7a88 R08: 0002000300004058 R09: ffff8881144a9f88
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881141d4000
R13: ffff888137dd7c68 R14: ffff888137dd7d58 R15: ffff888137dd7cc0
FS:  00007f4644f2a4c0(0000) GS:ffff8887a2d40000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055b4500f4380 CR3: 0000000114f7a003 CR4: 0000000000170ea0
Call Trace:
  simple_recursive_removal+0x33/0x2e0
  ? debugfs_remove+0x60/0x60
  debugfs_remove+0x40/0x60
  mlx5_debug_cq_remove+0x32/0x70 [mlx5_core]
  mlx5_core_destroy_cq+0x41/0x1d0 [mlx5_core]
  devx_obj_cleanup+0x151/0x330 [mlx5_ib]
  ? __pollwait+0xd0/0xd0
  ? xas_load+0x5/0x70
  ? xa_load+0x62/0xa0
  destroy_hw_idr_uobject+0x20/0x80 [ib_uverbs]
  uverbs_destroy_uobject+0x3b/0x360 [ib_uverbs]
  uobj_destroy+0x54/0xa0 [ib_uverbs]
  ib_uverbs_cmd_verbs+0xaf2/0x1160 [ib_uverbs]
  ? uverbs_finalize_object+0xd0/0xd0 [ib_uverbs]
  ib_uverbs_ioctl+0xc4/0x1b0 [ib_uverbs]
  __x64_sys_ioctl+0x3e4/0x8e0

## Which versions are affected by CVE-2021-47197?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47197?

Apply the vendor's patch.

## Is CVE-2021-47197 being exploited?

There is no known exploitation of CVE-2021-47197 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-2021-47197 and fix it if it is affected.

What it is: CVE-2021-47197 is a high-severity vulnerability in Linux kernel, published on 10 Apr 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-2021-47197 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-2021-47197/ (Markdown: https://insights.sbomify.com/CVE-2021-47197/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47197
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47197
- OSV: https://osv.dev/vulnerability/CVE-2021-47197

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47197/
Summaries are generated and may contain mistakes; the official description above is the record.