CVE-2026-64232: block: recompute nr_integrity_segments in blk_insert_cloned_request

From: Greg Kroah-Hartman <[email protected]>

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

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

block: recompute nr_integrity_segments in blk_insert_cloned_request

blk_insert_cloned_request() already recomputes nr_phys_segments
against the bottom queue, because "the queue settings related to
segment counting may differ from the original queue." The exact same
reasoning applies to integrity segments: a stacked driver's underlying
queue can have tighter virt_boundary_mask, seg_boundary_mask, or
max_segment_size than the top queue, in which case
blk_rq_count_integrity_sg() against the bottom queue produces a
different count than the cached rq->nr_integrity_segments inherited
from the source request by blk_rq_prep_clone().

When the cached count is lower than the bottom queue's actual count,
blk_rq_map_integrity_sg() trips

	BUG_ON(segments > rq->nr_integrity_segments);

on dispatch. The same families of stacked setups that motivated the
existing nr_phys_segments recompute -- dm-multipath fanning out to
nvme-rdma in particular -- can produce this.

Mirror the nr_phys_segments handling: when the request carries
integrity, recompute nr_integrity_segments against the bottom queue
and reject the request if it exceeds the bottom queue's
max_integrity_segments. blk_rq_count_integrity_sg() and
queue_max_integrity_segments() are both already available via
<linux/blk-integrity.h>, which blk-mq.c includes.

This closes a latent gap in the stacking contract and brings the
integrity-segment accounting in line with the existing
phys-segment accounting.

The Linux kernel CVE team has assigned CVE-2026-64232 to this issue.


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

	Issue introduced in 6.12 with commit 76c313f658d2752e8527610677164aa7094ef7a5 and fixed in 6.12.92 with commit 53a01bcc0242590eda4c452a5bd996f62457113b
	Issue introduced in 6.12 with commit 76c313f658d2752e8527610677164aa7094ef7a5 and fixed in 6.18.34 with commit 0943f81e1b3176f27dbaf6db268fc69d8a94f0ba
	Issue introduced in 6.12 with commit 76c313f658d2752e8527610677164aa7094ef7a5 and fixed in 7.0.11 with commit 42929c98d044f126508baf54a65b0f87f932fa75
	Issue introduced in 6.12 with commit 76c313f658d2752e8527610677164aa7094ef7a5 and fixed in 7.1 with commit 2c6e6a18a37b905cb584eb0dda3ae482162a81ca

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-2026-64232
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:
	block/blk-mq.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/53a01bcc0242590eda4c452a5bd996f62457113b
	https://git.kernel.org/stable/c/0943f81e1b3176f27dbaf6db268fc69d8a94f0ba
	https://git.kernel.org/stable/c/42929c98d044f126508baf54a65b0f87f932fa75
	https://git.kernel.org/stable/c/2c6e6a18a37b905cb584eb0dda3ae482162a81ca