CVE-2026-89456: s390/dasd: Propagate partial completion length across ERP recovery

CVE-2026-89456: s390/dasd: Propagate partial completion length across ERP recovery

[Greg Kroah-Hartman]

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

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

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

s390/dasd: Propagate partial completion length across ERP recovery

dasd_default_erp_postaction() copies the timing and device state from
the finished ERP request back to the original request but drops
proc_bytes. A request that was partially completed, an ESE read of a
not-yet-allocated track returns fewer bytes than requested, and then
recovered through the ERP chain loses its partial-completion length.
__dasd_cleanup_cqr() then sees proc_bytes == 0 and completes the whole
request instead of requeueing the remainder, silently returning zeroed
data for the part that was never read.

Carry proc_bytes over to the original request like the other
per-request state.

The Linux kernel CVE team has assigned CVE-2026-89456 to this issue.


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

	Issue introduced in 5.6 with commit 5e6bdd37c5526ef01326df5dabb93011ee89237e and fixed in 6.12.109 with commit d6b8778b1b82aa3a8dbf8612080f635b834bd16b
	Issue introduced in 5.6 with commit 5e6bdd37c5526ef01326df5dabb93011ee89237e and fixed in 6.18.50 with commit ceafb262475ac6cb3a7d07b1102608be2b216b99
	Issue introduced in 5.6 with commit 5e6bdd37c5526ef01326df5dabb93011ee89237e and fixed in 7.2.4 with commit 15ec03452c18e8d288e519837d21b308300d74b2
	Issue introduced in 5.6 with commit 5e6bdd37c5526ef01326df5dabb93011ee89237e and fixed in 7.3-rc1 with commit 6fb5ba2e7e43173a3761e46f091070a8185efa14
	Issue introduced in 5.4.26 with commit fbbacd0dcbc3ae9398c569dbea96ae4b5ad97e04
	Issue introduced in 5.5.10 with commit 5f7c9989f11305aaa43e0f4378f4f070022a9f2b

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-2026-89456
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/s390/block/dasd_erp.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/d6b8778b1b82aa3a8dbf8612080f635b834bd16b
	https://git.kernel.org/stable/c/ceafb262475ac6cb3a7d07b1102608be2b216b99
	https://git.kernel.org/stable/c/15ec03452c18e8d288e519837d21b308300d74b2
	https://git.kernel.org/stable/c/6fb5ba2e7e43173a3761e46f091070a8185efa14