Bug 2356667 (CVE-2025-21900)

Summary: CVE-2025-21900 kernel: NFSv4: Fix a deadlock when recovering state on a sillyrenamed file
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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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 2025-04-01 16:05:11 UTC 
In the Linux kernel, the following vulnerability has been resolved:

NFSv4: Fix a deadlock when recovering state on a sillyrenamed file

If the file is sillyrenamed, and slated for delete on close, it is
possible for a server reboot to triggeer an open reclaim, with can again
race with the application call to close(). When that happens, the call
to put_nfs_open_context() can trigger a synchronous delegreturn call
which deadlocks because it is not marked as privileged.

Instead, ensure that the call to nfs4_inode_return_delegation_on_close()
catches the delegreturn, and schedules it asynchronously.
Comment 1 Robb Gatica 2025-04-01 23:25:30 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025040133-CVE-2025-21900-8d31@gregkh/T