Bug 2348523 (CVE-2025-21795)

Summary: CVE-2025-21795 kernel: NFSD: fix hang in nfsd4_shutdown_callback
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
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Hardware: All   
OS: Linux   
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Description OSIDB Bzimport 2025-02-27 03:01:49 UTC 
In the Linux kernel, the following vulnerability has been resolved:

NFSD: fix hang in nfsd4_shutdown_callback

If nfs4_client is in courtesy state then there is no point to send
the callback. This causes nfsd4_shutdown_callback to hang since
cl_cb_inflight is not 0. This hang lasts about 15 minutes until TCP
notifies NFSD that the connection was dropped.

This patch modifies nfsd4_run_cb_work to skip the RPC call if
nfs4_client is in courtesy state.
Comment 1 Mauro Matteo Cascella 2025-02-27 17:05:44 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025022610-CVE-2025-21795-785d@gregkh/T