linux-cve-announce - CVE-2025-71090: nfsd: fix nfsd_file reference leak in nfsd4_add_rdaccess_to

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Message-ID: <2026011341-CVE-2025-71090-6e3a@gregkh>
Date: Tue, 13 Jan 2026 16:35:49 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-71090: nfsd: fix nfsd_file reference leak in nfsd4_add_rdaccess_to_wrdeleg()

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

In the Linux kernel, the following vulnerability has been resolved:

nfsd: fix nfsd_file reference leak in nfsd4_add_rdaccess_to_wrdeleg()

nfsd4_add_rdaccess_to_wrdeleg() unconditionally overwrites
fp->fi_fds[O_RDONLY] with a newly acquired nfsd_file. However, if
the client already has a SHARE_ACCESS_READ open from a previous OPEN
operation, this action overwrites the existing pointer without
releasing its reference, orphaning the previous reference.

Additionally, the function originally stored the same nfsd_file
pointer in both fp->fi_fds[O_RDONLY] and fp->fi_rdeleg_file with
only a single reference. When put_deleg_file() runs, it clears
fi_rdeleg_file and calls nfs4_file_put_access() to release the file.

However, nfs4_file_put_access() only releases fi_fds[O_RDONLY] when
the fi_access[O_RDONLY] counter drops to zero. If another READ open
exists on the file, the counter remains elevated and the nfsd_file
reference from the delegation is never released. This potentially
causes open conflicts on that file.

Then, on server shutdown, these leaks cause __nfsd_file_cache_purge()
to encounter files with an elevated reference count that cannot be
cleaned up, ultimately triggering a BUG() in kmem_cache_destroy()
because there are still nfsd_file objects allocated in that cache.

The Linux kernel CVE team has assigned CVE-2025-71090 to this issue.

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

	Issue introduced in 6.17 with commit e7a8ebc305f26cab608e59a916a4ae89d6656c5f and fixed in 6.18.4 with commit c07dc84ed67c5a182273171639bacbbb87c12175
	Issue introduced in 6.17 with commit e7a8ebc305f26cab608e59a916a4ae89d6656c5f and fixed in 6.19-rc4 with commit 8072e34e1387d03102b788677d491e2bcceef6f5

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-2025-71090
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/nfsd/nfs4state.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/c07dc84ed67c5a182273171639bacbbb87c12175
	https://git.kernel.org/stable/c/8072e34e1387d03102b788677d491e2bcceef6f5