CVE-2026-64053: block: don't overwrite bip_vcnt in bio_integrity_copy_user()

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

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

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

block: don't overwrite bip_vcnt in bio_integrity_copy_user()

bio_integrity_add_page() already sets bip_vcnt to 1 for the bounce
segment. Overwriting it with nr_vecs breaks bip_vcnt <= bip_max_vcnt
on WRITE (bip_max_vcnt is 1), so the gap-merge checks in block/blk.h
read past the bip_vec[] flex array. On READ the read is in bounds
but lands on a saved user bvec instead of the bounce.

The line was added for split propagation, but bio_integrity_clone()
doesn't copy bip_vcnt and BIP_CLONE_FLAGS excludes BIP_COPY_USER.

The Linux kernel CVE team has assigned CVE-2026-64053 to this issue.


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

	Issue introduced in 6.11 with commit 3991657ae7074c3c497bf095093178bed37ea1b4 and fixed in 6.12.92 with commit d18160c9525c63c203656fefd847e94b538cd4a4
	Issue introduced in 6.11 with commit 3991657ae7074c3c497bf095093178bed37ea1b4 and fixed in 6.18.34 with commit 0d48654af4d1390c888389206cc13b51b82c30e6
	Issue introduced in 6.11 with commit 3991657ae7074c3c497bf095093178bed37ea1b4 and fixed in 7.0.11 with commit 066be1439593a381b1a29663becfcfe0c92363e7
	Issue introduced in 6.11 with commit 3991657ae7074c3c497bf095093178bed37ea1b4 and fixed in 7.1 with commit 637ad3a56a3b889527d1dacea6fea2a8bd648140

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-2026-64053
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/bio-integrity.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/d18160c9525c63c203656fefd847e94b538cd4a4
	https://git.kernel.org/stable/c/0d48654af4d1390c888389206cc13b51b82c30e6
	https://git.kernel.org/stable/c/066be1439593a381b1a29663becfcfe0c92363e7
	https://git.kernel.org/stable/c/637ad3a56a3b889527d1dacea6fea2a8bd648140