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

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

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

atascsiwritesamexlat() 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 ataformatdsmtrimdescr() into the 2048-byte atascsirbuf staging buffer, and the number of bytes copied is compared against the logical sector size by the caller:

size = ataformatdsmtrimdescr(scmd, trmax, block, nblock); if (size != len) / len == sdp->sectorsize / goto invalidparamlen;

ataformatdsmtrimdescr() clamps the copy length to ATASCSIRBUFSIZE (2048). On a device whose logical sector size exceeds that (e.g. a 4Kn device, where sectorsize == 4096) the function can never return more than 2048, while the caller expects it to return sectorsize. The comparison therefore always fails, so every TRIM is rejected with "Parameter list length error" and WARNON() 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 ATAMAXTRIMRNUM (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 ATAMAXTRIMRNUM 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.