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CVE Record

CVE-2022-48721: net/smc: Forward wakeup to smc socket waitqueue after fallback

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: <IRQ> __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 </IRQ> <TASK> 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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel bug can crash affected systems when SMC sockets fall back to TCP/IP while applications still have waitqueue entries on the SMC socket. The source describes a kernel general protection fault, so the business risk is availability disruption rather than confirmed data theft or remote code execution.

Executive priority

Treat this as a stability and uptime issue. Patch through normal kernel maintenance, faster for systems using SMC or hosting critical services. There is no source-backed evidence here requiring emergency incident response for active exploitation.

Technical view

The flaw is in net/smc fallback handling. Older logic privately moved waitqueue entries from the SMC socket to the TCP clcsock waitqueue, breaking synchronization for owners such as epoll. The fix stops transferring entries and forwards clcsock wakeups back to the SMC socket waitqueue when needed.

Likely exposure

Exposure is most likely on Linux systems using SMC socket functionality and affected kernel builds listed in the CVE data, including 5.16-era and related stable branches. Systems not using SMC are less likely to encounter the described crash path, but kernel package status should still be verified.

Exploitation context

The bundle marks KEV as false and provides no cited evidence of active exploitation. The described failure requires SMC-to-TCP fallback with remaining waitqueue entries, such as epoll entries. The documented consequence is a kernel crash, not a confirmed privilege escalation or data compromise.

Researcher notes

The core issue is waitqueue ownership and locking after SMC fallback. Validation should focus on kernel provenance, SMC usage, and crash signatures. The CVE metadata lacks CVSS, CWE, and exploit evidence, so severity confidence is limited.

Mitigation direction

  • Apply supported Linux distribution kernel updates containing the referenced stable fixes.
  • Check vendor advisories before relying on upstream commit status alone.
  • Prioritize systems where SMC sockets are enabled or used by production workloads.
  • If updates are unavailable, ask the vendor for supported SMC risk-reduction guidance.

Validation and detection

  • Identify running kernel versions and compare them with vendor-fixed kernel packages.
  • Confirm the deployed kernel includes the referenced stable fix commits where applicable.
  • Check whether SMC support is enabled and used on exposed systems.
  • Review kernel logs for related general protection faults or SMC fallback crashes.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2022-48721 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
4Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxfb92e025baa73e99250b79ab64f4e088d2888993, 2153bd1e3d3dbf6a3403572084ef6ed31c53c5f0, 2153bd1e3d3dbf6a3403572084ef6ed31c53c5f0, d6e981ec9491be5ec46d838b1151e7edefe607f5, ff6eeb627898c179aac421af5d6515d3f50b84df, 5.15.7, 5.4.164, 5.10.84unaffected
LinuxLinux5.16, 0, 5.15.22, 5.16.8, 5.17affected
Weakness

CWE details

No CWE listed

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