linux-cve-announce - CVE-2025-40046: io_uring/zcrx: fix overshooting recv limit

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Message-ID: <2025102813-CVE-2025-40046-391f@gregkh>
Date: Tue, 28 Oct 2025 12:48:23 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40046: io_uring/zcrx: fix overshooting recv limit

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

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

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

io_uring/zcrx: fix overshooting recv limit

It's reported that sometimes a zcrx request can receive more than was
requested. It's caused by io_zcrx_recv_skb() adjusting desc->count for
all received buffers including frag lists, but then doing recursive
calls to process frag list skbs, which leads to desc->count double
accounting and underflow.

The Linux kernel CVE team has assigned CVE-2025-40046 to this issue.


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

	Issue introduced in 6.15 with commit 6699ec9a23f85f1764183430209c741847c45f12 and fixed in 6.17.3 with commit 8bcc9eaf1b19f1a7029cba19f6bd4122b40f6c4f
	Issue introduced in 6.15 with commit 6699ec9a23f85f1764183430209c741847c45f12 and fixed in 6.18-rc1 with commit 09cfd3c52ea76f43b3cb15e570aeddf633d65e80

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-2025-40046
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:
	io_uring/zcrx.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/8bcc9eaf1b19f1a7029cba19f6bd4122b40f6c4f
	https://git.kernel.org/stable/c/09cfd3c52ea76f43b3cb15e570aeddf633d65e80