linux-cve-announce - CVE-2025-21900: NFSv4: Fix a deadlock when recovering state on a sillyrenamed file

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Message-ID: <2025040133-CVE-2025-21900-8d31@gregkh>
Date: Tue,  1 Apr 2025 16:25:36 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21900: NFSv4: Fix a deadlock when recovering state on a sillyrenamed file

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2025-21900 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.11 with commit adb4b42d19aea91826621a8d0bac94cf2c08f8bc and fixed in 6.12.18 with commit 4fe4ae6c2e01d028856b73b6328b12b8945df871
	Issue introduced in 6.11 with commit adb4b42d19aea91826621a8d0bac94cf2c08f8bc and fixed in 6.13.6 with commit f41a60bc43e7abbc636fee78bed0d74c31e738b0
	Issue introduced in 6.11 with commit adb4b42d19aea91826621a8d0bac94cf2c08f8bc and fixed in 6.14 with commit 8f8df955f078e1a023ee55161935000a67651f38

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-21900
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/nfs/delegation.c
	fs/nfs/delegation.h
	fs/nfs/nfs4proc.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/4fe4ae6c2e01d028856b73b6328b12b8945df871
	https://git.kernel.org/stable/c/f41a60bc43e7abbc636fee78bed0d74c31e738b0
	https://git.kernel.org/stable/c/8f8df955f078e1a023ee55161935000a67651f38