linux-cve-announce - CVE-2025-37882: usb: xhci: Fix isochronous Ring Underrun/Overrun event handling

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Message-ID: <2025050944-CVE-2025-37882-db64@gregkh>
Date: Fri,  9 May 2025 08:45:49 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-37882: usb: xhci: Fix isochronous Ring Underrun/Overrun event handling

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

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

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

usb: xhci: Fix isochronous Ring Underrun/Overrun event handling

The TRB pointer of these events points at enqueue at the time of error
occurrence on xHCI 1.1+ HCs or it's NULL on older ones. By the time we
are handling the event, a new TD may be queued at this ring position.

I can trigger this race by rising interrupt moderation to increase IRQ
handling delay. Similar delay may occur naturally due to system load.

If this ever happens after a Missed Service Error, missed TDs will be
skipped and the new TD processed as if it matched the event. It could
be given back prematurely, risking data loss or buffer UAF by the xHC.

Don't complete TDs on xrun events and don't warn if queued TDs don't
match the event's TRB pointer, which can be NULL or a link/no-op TRB.
Don't warn if there are no queued TDs at all.

Now that it's safe, also handle xrun events if the skip flag is clear.
This ensures completion of any TD stuck in 'error mid TD' state right
before the xrun event, which could happen if a driver submits a finite
number of URBs to a buggy HC and then an error occurs on the last TD.

The Linux kernel CVE team has assigned CVE-2025-37882 to this issue.

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

	Fixed in 6.12.26 with commit 16a7a8e6c47fea5c847beb696c8c21a7a44c1915
	Fixed in 6.14.5 with commit 39a080a2925c81b0f1da0add44722ef2b78e5454
	Fixed in 6.15-rc1 with commit 906dec15b9b321b546fd31a3c99ffc13724c7af4

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-2025-37882
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:
	drivers/usb/host/xhci-ring.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/16a7a8e6c47fea5c847beb696c8c21a7a44c1915
	https://git.kernel.org/stable/c/39a080a2925c81b0f1da0add44722ef2b78e5454
	https://git.kernel.org/stable/c/906dec15b9b321b546fd31a3c99ffc13724c7af4