CVE-2026-98232: scsi: core: Validate MODE SENSE lengths in scsi_cdl_enable()

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

scsi: core: Validate MODE SENSE lengths in scsicdlenable()

scsicdlenable() uses length fields returned by MODE SENSE to locate the ATA feature mode page in a 64-byte stack buffer. A target can report a total length shorter than its mode header and block descriptors. The unsigned subtraction used for the MODE SELECT length can wrap, and the separately computed bufdata can point beyond buf.

During automatic scan, enable is false, so the read-modify-write of bufdata[4] can clear the low two bits of a target-selected out-of-bounds stack byte. scsimodeselect() can then copy up to 64 bytes from outside the buffer into the outgoing MODE SELECT payload, disclosing stack contents to the target.

This is reachable while scanning a USB storage device that identifies as an ATA device and advertises CDL support. No filesystem mount or userspace access to the block device is required.

On upstream commit cee9395acd80 ("Linux 7.3-rc1"), a build-specific, one-vCPU QEMU/Raw Gadget proof using QEMU-only multi-UDC allocator sampling executed a fixed proof command inside the guest and created a UID-0-owned marker during automatic enumeration, with KASLR and NX enabled.

The issue was independently found during security research at Drivesec S.r.l.

Cap the available length to the buffer size. Validate and consume the mode header and block descriptor lengths before using the page, and require the five bytes needed to access the CDL field.