# CVE-2022-48721: net/smc: Forward wakeup to smc socket waitqueue after fallback
> A flaw in the Linux kernel's SMC protocol handling causes a crash when waitqueue entries are improperly transferred during TCP fallback, leading to denial of service.
- **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:** 20 Jun 2024
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2022-48721, GHSA-cw8x-f629-7c3v, ROOT-OS-DEBIAN-11-CVE-2022-48721, UBUNTU-CVE-2022-48721
## What is CVE-2022-48721?
CVE-2022-48721 is a high-severity vulnerability in Linux kernel, published on 20 Jun 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/smc: Forward wakeup to smc socket waitqueue after fallback
When we replace TCP with SMC and a fallback occurs, there may be
some socket waitqueue entries remaining in smc socket->wq, such
as eppoll_entries inserted by userspace applications.
After the fallback, data flows over TCP/IP and only clcsocket->wq
will be woken up. Applications can't be notified by the entries
which were inserted in smc socket->wq before fallback. So we need
a mechanism to wake up smc socket->wq at the same time if some
entries remaining in it.
The current workaround is to transfer the entries from smc socket->wq
to clcsock->wq during the fallback. But this may cause a crash
like this:
general protection fault, probably for non-canonical address 0xdead000000000100: 0000 [#1] PREEMPT SMP PTI
CPU: 3 PID: 0 Comm: swapper/3 Kdump: loaded Tainted: G E 5.16.0+ #107
RIP: 0010:__wake_up_common+0x65/0x170
Call Trace:
__wake_up_common_lock+0x7a/0xc0
sock_def_readable+0x3c/0x70
tcp_data_queue+0x4a7/0xc40
tcp_rcv_established+0x32f/0x660
? sk_filter_trim_cap+0xcb/0x2e0
tcp_v4_do_rcv+0x10b/0x260
tcp_v4_rcv+0xd2a/0xde0
ip_protocol_deliver_rcu+0x3b/0x1d0
ip_local_deliver_finish+0x54/0x60
ip_local_deliver+0x6a/0x110
? tcp_v4_early_demux+0xa2/0x140
? tcp_v4_early_demux+0x10d/0x140
ip_sublist_rcv_finish+0x49/0x60
ip_sublist_rcv+0x19d/0x230
ip_list_rcv+0x13e/0x170
__netif_receive_skb_list_core+0x1c2/0x240
netif_receive_skb_list_internal+0x1e6/0x320
napi_complete_done+0x11d/0x190
mlx5e_napi_poll+0x163/0x6b0 [mlx5_core]
__napi_poll+0x3c/0x1b0
net_rx_action+0x27c/0x300
__do_softirq+0x114/0x2d2
irq_exit_rcu+0xb4/0xe0
common_interrupt+0xba/0xe0
The crash is caused by privately transferring waitqueue entries from
smc socket->wq to clcsock->wq. The owners of these entries, such as
epoll, have no idea that the entries have been transferred to a
different socket wait queue and still use original waitqueue spinlock
(smc socket->wq.wait.lock) to make the entries operation exclusive,
but it doesn't work. The operations to the entries, such as removing
from the waitqueue (now is clcsock->wq after fallback), may cause a
crash when clcsock waitqueue is being iterated over at the moment.
This patch tries to fix this by no longer transferring wait queue
entries privately, but introducing own implementations of clcsock's
callback functions in fallback situation. The callback functions will
forward the wakeup to smc socket->wq if clcsock->wq is actually woken
up and smc socket->wq has remaining entries.
## Which versions are affected by CVE-2022-48721?
It affects 1 product.
Products: Linux kernel.
## How do I fix CVE-2022-48721?
Apply the vendor's patch.
## Is CVE-2022-48721 being exploited?
There is no known exploitation of CVE-2022-48721 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-2022-48721 and fix it if it is affected.
What it is: CVE-2022-48721 is a high-severity vulnerability in Linux kernel, published on 20 Jun 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-2022-48721 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-2022-48721/ (Markdown: https://insights.sbomify.com/CVE-2022-48721/index.md)
```
## Sources
- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-48721
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-48721
- OSV: https://osv.dev/vulnerability/CVE-2022-48721
---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-48721/
Summaries are generated and may contain mistakes; the official description above is the record.