linux-cve-announce - CVE-2023-53606: nfsd: clean up potential nfsd

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Message-ID: <2025100432-CVE-2023-53606-8c1a@gregkh>
Date: Sat,  4 Oct 2025 17:52:00 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53606: nfsd: clean up potential nfsd_file refcount leaks in COPY codepath

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

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

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

nfsd: clean up potential nfsd_file refcount leaks in COPY codepath

There are two different flavors of the nfsd4_copy struct. One is
embedded in the compound and is used directly in synchronous copies. The
other is dynamically allocated, refcounted and tracked in the client
struture. For the embedded one, the cleanup just involves releasing any
nfsd_files held on its behalf. For the async one, the cleanup is a bit
more involved, and we need to dequeue it from lists, unhash it, etc.

There is at least one potential refcount leak in this code now. If the
kthread_create call fails, then both the src and dst nfsd_files in the
original nfsd4_copy object are leaked.

The cleanup in this codepath is also sort of weird. In the async copy
case, we'll have up to four nfsd_file references (src and dst for both
flavors of copy structure). They are both put at the end of
nfsd4_do_async_copy, even though the ones held on behalf of the embedded
one outlive that structure.

Change it so that we always clean up the nfsd_file refs held by the
embedded copy structure before nfsd4_copy returns. Rework
cleanup_async_copy to handle both inter and intra copies. Eliminate
nfsd4_cleanup_intra_ssc since it now becomes a no-op.

The Linux kernel CVE team has assigned CVE-2023-53606 to this issue.

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

	Fixed in 5.10.220 with commit fd63299db8090307eae66f2aef17c8f00aafa0a9
	Fixed in 5.15.154 with commit b3169b6ffe036b549c296a9e71591d29a1fb3209
	Fixed in 6.1.16 with commit 75b8c681c563ef7e85da6862354efc18d2a08b1b
	Fixed in 6.2.3 with commit 8f565846fbe8182961498d4cbe618b15076a683b
	Fixed in 6.3 with commit 6ba434cb1a8d403ea9aad1b667c3ea3ad8b3191f

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-2023-53606
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/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/fd63299db8090307eae66f2aef17c8f00aafa0a9
	https://git.kernel.org/stable/c/b3169b6ffe036b549c296a9e71591d29a1fb3209
	https://git.kernel.org/stable/c/75b8c681c563ef7e85da6862354efc18d2a08b1b
	https://git.kernel.org/stable/c/8f565846fbe8182961498d4cbe618b15076a683b
	https://git.kernel.org/stable/c/6ba434cb1a8d403ea9aad1b667c3ea3ad8b3191f