Bug 2388942 (CVE-2025-38552)

Summary: CVE-2025-38552 kernel: mptcp: plug races between subflow fail and subflow creation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-08-16 12:02:50 UTC 
In the Linux kernel, the following vulnerability has been resolved:

mptcp: plug races between subflow fail and subflow creation

We have races similar to the one addressed by the previous patch between
subflow failing and additional subflow creation. They are just harder to
trigger.

The solution is similar. Use a separate flag to track the condition
'socket state prevent any additional subflow creation' protected by the
fallback lock.

The socket fallback makes such flag true, and also receiving or sending
an MP_FAIL option.

The field 'allow_infinite_fallback' is now always touched under the
relevant lock, we can drop the ONCE annotation on write.
Comment 1 Alexander B 2025-08-18 09:08:21 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025081629-CVE-2025-38552-f7a9@gregkh/T