CVE-2025-38492 Information

Jul 29, 2025 cve

Description

In the Linux kernel the following vulnerability has been resolved:

netfs: Fix race between cache write completion and ALL_QUEUED being set

When netfslib is issuing subrequests the subrequests start processing immediately and may complete before we reach the end of the issuing function. At the end of the issuing function we set NETFS_RREQ_ALL_QUEUED to indicate to the collector that we aren’t going to issue any more subreqs and that it can do the final notifications and cleanup.

Now this isn’t a problem if the request is synchronous (NETFS_RREQ_OFFLOAD_COLLECTION is unset) as the result collection will be done in-thread and we’re guaranteed an opportunity to run the collector.

However if the request is asynchronous collection is primarily triggered by the termination of subrequests queuing it on a workqueue. Now a race can occur here if the app thread sets ALL_QUEUED after the last subrequest terminates.

This can happen most easily with the copy2cache code (as used by Ceph) where in the collection routine of a read request an asynchronous write request is spawned to copy data to the cache. Folios are added to the write request as they’re unlocked but there may be a delay before ALL_QUEUED is set as the write subrequests may complete before we get there.

If all the write subreqs have finished by the ALL_QUEUED point no further events happen and the collection never happens leaving the request hanging.

Fix this by queuing the collector after setting ALL_QUEUED. This is a bit heavy-handed and it may be sufficient to do it only if there are no extant subreqs.

Also add a tracepoint to cross-reference both requests in a copy-to-request operation and add a trace to the netfs_rreq tracepoint to indicate the setting of ALL_QUEUED.

Reference

https://git.kernel.org/stable/c/110188a13c4853bd4c342e600ced4dfd26c3feb5 https://git.kernel.org/stable/c/89635eae076cd8eaa5cb752f66538c9dc6c9fdc3

CNNVD-202507-3472 (Published: 2025-07-28)

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