nvmet: copy the hostid into the ctrl before creating PR pc_refs

Overview

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

nvmet: copy the hostid into the ctrl before creating PR pc_refs

Commit 6202783184bf ("nvmet: Improve nvmet_alloc_ctrl() interface and implementation") added a second uuid_copy() of args->hostid near the end of nvmet_alloc_ctrl(), and commit 7b658153f1b8 ("nvmet: Remove duplicate uuid_copy") removed the original copy that sat before nvmet_ctrl_init_pr() instead of the new one.

Since then nvmet_ctrl_init_pr() snapshots ctrl->hostid into the per-controller per-namespace reservation refs while the uuid_copy() from the connect data runs later, after the controller is published. The ctrl is allocated with kzalloc(), so every pc_ref created on this path stores the nil UUID.

pc_ref->hostid has a single consumer: nvmet_pr_set_ctrl_to_abort() matches it against the preempted registrant's hostid to kill and drain the victim's in-flight I/O for Preempt and Abort. The match can never hit with the nil UUID, so whenever a namespace with reservations enabled exists before a host connects, which includes every reconnect, Preempt and Abort silently degrades into a plain Preempt: the preempting host sees success while the victim's in-flight I/O is still in the air.

Copy the hostid where the rest of the connect data is consumed, before the controller is published and before nvmet_ctrl_init_pr() takes its snapshot.

Affected

• Linux >= 7b658153f1b8a79ed98980f2fef7b92a66aeb9cd < d3d6d7efdacc08616d23b3ac42272a494951dc0f
• Linux >= 7b658153f1b8a79ed98980f2fef7b92a66aeb9cd < 23194531595c5d1d4454e3a607b0c8fc0c4e8695
• Linux >= 7b658153f1b8a79ed98980f2fef7b92a66aeb9cd < 5211fed41d7ec90e9ab7239dc4bffffe4d0b2b62
• Linux 6.15

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.