nvmet: pci-epf: reject too-short SGL segments

Overview

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

nvmet: pci-epf: reject too-short SGL segments

The host controls an SGL segment's length. A nonzero length smaller than one SGL descriptor makes nr_descs zero, so nvmet_pci_epf_get_sgl_segment() reads the type byte of sgls[-1] outside the allocated buffer. If that byte contains a segment descriptor type, the function also copies the preceding 16 bytes and returns a negative descriptor count.

The read was reproduced in 3/3 KASAN boots with only the host transfer mocked by a KUnit test:

BUG: KASAN: slab-out-of-bounds in nvmet_pci_epf_get_sgl_segment Read of size 1 by task kunit_try_catch Call Trace: nvmet_pci_epf_get_sgl_segment nvmet_pci_epf_short_sgl_test Kernel panic - not syncing: KASAN: panic_on_warn set ...

Reject segments that cannot hold one descriptor before allocating or transferring their contents.

Affected

• Linux >= 0faa0fe6f90ea59b10d1b0f15ce0eb0c18eff186 < 2423a05dd0f21330c47ce0ae1cb54a8b0be821e2
• Linux >= 0faa0fe6f90ea59b10d1b0f15ce0eb0c18eff186 < 472df1d103dbe3e9d09156f0667e36180e912c46
• Linux >= 0faa0fe6f90ea59b10d1b0f15ce0eb0c18eff186 < 5d5fbfbbacd1efb13a9bf91317d4fde859ede4b9
• Linux 6.14

Remediation

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