linux-cve-announce - CVE-2022-50487: NFSD: Protect against send buffer overflow in NFSv3 READDIR

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Message-ID: <2025100441-CVE-2022-50487-f5ea@gregkh>
Date: Sat,  4 Oct 2025 17:16:46 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50487: NFSD: Protect against send buffer overflow in NFSv3 READDIR

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

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

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

NFSD: Protect against send buffer overflow in NFSv3 READDIR

Since before the git era, NFSD has conserved the number of pages
held by each nfsd thread by combining the RPC receive and send
buffers into a single array of pages. This works because there are
no cases where an operation needs a large RPC Call message and a
large RPC Reply message at the same time.

Once an RPC Call has been received, svc_process() updates
svc_rqst::rq_res to describe the part of rq_pages that can be
used for constructing the Reply. This means that the send buffer
(rq_res) shrinks when the received RPC record containing the RPC
Call is large.

A client can force this shrinkage on TCP by sending a correctly-
formed RPC Call header contained in an RPC record that is
excessively large. The full maximum payload size cannot be
constructed in that case.

Thanks to Aleksi Illikainen and Kari Hulkko for uncovering this
issue.

The Linux kernel CVE team has assigned CVE-2022-50487 to this issue.

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

	Fixed in 5.10.220 with commit 57774b1526163766403167b7bf00b136fb103761
	Fixed in 5.15.75 with commit 071a076fd1b763aa6fe478efa047e0a549ba9c22
	Fixed in 5.19.17 with commit 9c3224826ec17f14e8bdfc86cb7e82fe52d744a7
	Fixed in 6.0.3 with commit 279274e31270c28b86feffe5e166d4088f22317b
	Fixed in 6.1 with commit 640f87c190e0d1b2a0fcb2ecf6d2cd53b1c41991

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-2022-50487
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/nfs3proc.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/57774b1526163766403167b7bf00b136fb103761
	https://git.kernel.org/stable/c/071a076fd1b763aa6fe478efa047e0a549ba9c22
	https://git.kernel.org/stable/c/9c3224826ec17f14e8bdfc86cb7e82fe52d744a7
	https://git.kernel.org/stable/c/279274e31270c28b86feffe5e166d4088f22317b
	https://git.kernel.org/stable/c/640f87c190e0d1b2a0fcb2ecf6d2cd53b1c41991