Linux Kernel CVE-2025-40118

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

scsi: pm80xx: Fix array-index-out-of-of-bounds on rmmod

Since commit f7b705c238d1 ("scsi: pm80xx: Set phy_attached to zero when device is gone") UBSAN reports:

UBSAN: array-index-out-of-bounds in drivers/scsi/pm8001/pm8001_sas.c:786:17 index 28 is out of range for type 'pm8001_phy [16]'

on rmmod when using an expander.

For a direct attached device, attached_phy contains the local phy id. For a device behind an expander, attached_phy contains the remote phy id, not the local phy id.

I.e. while pm8001_ha will have pm8001_ha->chip->n_phy local phys, for a device behind an expander, attached_phy can be much larger than pm8001_ha->chip->n_phy (depending on the amount of phys of the expander).

E.g. on my system pm8001_ha has 8 phys with phy ids 0-7. One of the ports has an expander connected. The expander has 31 phys with phy ids 0-30.

The pm8001_ha->phy array only contains the phys of the HBA. It does not contain the phys of the expander. Thus, it is wrong to use attached_phy to index the pm8001_ha->phy array for a device behind an expander.

Thus, we can only clear phy_attached for devices that are directly attached.

The Linux kernel's pm80xx SCSI driver is affected on any version carrying commit f7b705c238d1 ('scsi: pm80xx: Set phy_attached to zero when device is gone') up to the fixes. The vulnerable code path is only reachable on systems using a pm80xx-supported SAS HBA with a SAS expander in the topology. No CPE strings were supplied in the intelligence; exact affected kernel version ranges should be taken from the Ubuntu advisories. Vendor/distributor advisories: Ubuntu USN-8126-1 (https://ubuntu.com/security/notices/USN-8126-1) and USN-8125-1 (https://ubuntu.com/security/notices/USN-8125-1), with upstream stable fixes at git.kernel.org.