High · published September 12, 2026
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.