CVE-2026-89586

Summary

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.

Affected Software

Weaknesses

References

• 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

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