linux-cve-announce - CVE-2025-40216: io_uring/rsrc: don't rely on user vaddr alignment

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Message-ID: <2025120417-CVE-2025-40216-d79f@gregkh>
Date: Thu,  4 Dec 2025 15:14:18 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40216: io_uring/rsrc: don't rely on user vaddr alignment

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

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

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

io_uring/rsrc: don't rely on user vaddr alignment

There is no guaranteed alignment for user pointers, however the
calculation of an offset of the first page into a folio after coalescing
uses some weird bit mask logic, get rid of it.

The Linux kernel CVE team has assigned CVE-2025-40216 to this issue.


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

	Issue introduced in 6.12 with commit a8edbb424b1391b077407c75d8f5d2ede77aa70d and fixed in 6.12.36 with commit 50998b0ae7d9d552e96d8b7239981cf05f65eff5
	Issue introduced in 6.12 with commit a8edbb424b1391b077407c75d8f5d2ede77aa70d and fixed in 6.15.5 with commit f16769241594be59387b56ab525e327f54377e60
	Issue introduced in 6.12 with commit a8edbb424b1391b077407c75d8f5d2ede77aa70d and fixed in 6.16 with commit 3a3c6d61577dbb23c09df3e21f6f9eda1ecd634b

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-2025-40216
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/rsrc.c
	io_uring/rsrc.h


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/50998b0ae7d9d552e96d8b7239981cf05f65eff5
	https://git.kernel.org/stable/c/f16769241594be59387b56ab525e327f54377e60
	https://git.kernel.org/stable/c/3a3c6d61577dbb23c09df3e21f6f9eda1ecd634b