CVE-2026-89586: ata: libata-scsi: fix DSM TRIM for sector sizes larger than 2048 bytes

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

ata: libata-scsi: fix DSM TRIM for sector sizes larger than 2048 bytes

ata_scsi_write_same_xlat() translates a SCSI WRITE SAME command with the
UNMAP bit set into an ATA DATA SET MANAGEMENT TRIM command.  The TRIM
descriptor is built by ata_format_dsm_trim_descr() into the 2048-byte
ata_scsi_rbuf staging buffer, and the number of bytes copied is compared
against the logical sector size by the caller:

	size = ata_format_dsm_trim_descr(scmd, trmax, block, n_block);
	if (size != len)		/* len == sdp->sector_size */
		goto invalid_param_len;

ata_format_dsm_trim_descr() clamps the copy length to ATA_SCSI_RBUF_SIZE
(2048).  On a device whose logical sector size exceeds that (e.g. a 4Kn
device, where sector_size == 4096) the function can never return more than
2048, while the caller expects it to return sector_size.  The comparison
therefore always fails, so every TRIM is rejected with "Parameter list
length error" and WARN_ON() splats on each attempt.  TRIM / discard is
thus completely broken on such devices.

The descriptor was incorrectly sized from the logical sector size.  A DSM
TRIM payload is a list of 512-byte pages, each holding up to
ATA_MAX_TRIM_RNUM (64) LBA Range Entries, and is independent of the logical
sector size.  The Block Limits VPD page already advertises a single such
page as the maximum WRITE SAME length (65535 * ATA_MAX_TRIM_RNUM logical
blocks), so the block layer never sends a request that needs more than one
page.

Emit exactly one 512-byte page, independent of the logical sector size,
and transfer only that page (COUNT == 1).  For a 512-byte-sector device
this is unchanged; devices with larger logical sectors now work instead of
failing every TRIM.

The Linux kernel CVE team has assigned CVE-2026-89586 to this issue.


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

	Issue introduced in 4.9 with commit ef2d7392c4ece5c3cd12a6c7ca9366cd8f189aff and fixed in 6.12.109 with commit 04e2befe25792f2e90097f284d7e86fc6bcfe928
	Issue introduced in 4.9 with commit ef2d7392c4ece5c3cd12a6c7ca9366cd8f189aff and fixed in 6.18.50 with commit c2e3dccd6870659851eaa4c12ab16418b8e3040a
	Issue introduced in 4.9 with commit ef2d7392c4ece5c3cd12a6c7ca9366cd8f189aff and fixed in 7.2.4 with commit 4a4268a0b0a595bd9534cf9c7fda93775a7d8a0d
	Issue introduced in 4.9 with commit ef2d7392c4ece5c3cd12a6c7ca9366cd8f189aff and fixed in 7.3-rc1 with commit 79cce911e623c0baa0fde307ce3a434e084b881a

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-2026-89586
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/ata/libata-scsi.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/04e2befe25792f2e90097f284d7e86fc6bcfe928
	https://git.kernel.org/stable/c/c2e3dccd6870659851eaa4c12ab16418b8e3040a
	https://git.kernel.org/stable/c/4a4268a0b0a595bd9534cf9c7fda93775a7d8a0d
	https://git.kernel.org/stable/c/79cce911e623c0baa0fde307ce3a434e084b881a