CVE-2026-98216

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

IB/hfi1: Fix the PIO_CRED credit-return mmap

hfi1_file_mmap()'s PIO_CRED case must hand user space the single

credit-return page that holds this context's entry. That page is the

second or third page of the per-node credit-return allocation once the

hardware send context index reaches 64 or 128, so the failure below is

intermittent: when the entry lands on the first page the offset is zero

and everything works.

Two things are wrong.

First, cr_page_offset is a byte offset but .va is a struct

credit_return *, so adding it is pointer arithmetic and scales the offset

by sizeof(struct credit_return) == 64. memvirt then lands 256 KiB or

512 KiB past a 10240-byte allocation. With an IOMMU translating, that

address is inside the vmalloc range but in no vm_area, so

dma_mmap_coherent() -> iommu_dma_mmap() finds no pages, vmalloc_to_pfn()

returns page_to_pfn(NULL), and remap_pfn_range() installs a frame above

MAXPHYADDR. The first user read then takes:

psm2_ep_open_pr: Corrupted page table at address 7a14d007e000

PGD 800000013886a067 P4D 800000013886a067 PUD 13886b067 PMD 13886c067

PTE 800049168e911235

Oops: Bad pagetable: 000d [#1] SMP PTI

Second, and still wrong once the arithmetic is corrected,

dma_mmap_coherent() describes a whole coherent buffer and selects the

page within it with vma->vm_pgoff. Offsetting cpu_addr has no effect:

for a vmap'd allocation iommu_dma_mmap() uses cpu_addr only to locate the

vm_area and then maps pages[vm_pgoff], which hfi1_file_mmap() has just

set to 0. User space therefore always receives the first credit-return

page, every credit read is for the wrong context, and send PIO stalls

forever.

Use the DMA API as intended: pass the base of the allocation with its

full length and select the page with vm_pgoff. A separate length is

needed because memlen must keep describing the VMA for the existing size

check. The dma-direct path stays correct as well, since dma_direct_mmap()

adds the same vm_pgoff to the base pfn.

Tested on a Dell T7610 (Xeon E5-2650 v2, Intel IOMMU in DMA-FQ mode)

against a Threadripper PRO 3995WX peer, both Omni-Path 100. Before this

change psm2_ep_open() Oopses the kernel; with only the arithmetic

corrected psm2_ep_open() succeeds but any transfer that uses send PIO

hangs, PSM2_SDMA=2 (send PIO disabled) completing normally while

PSM2_SDMA=0 (send PIO only) hangs every time. With this change send PIO,

send DMA and the default mixed mode all work.