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.
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.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
||||||||||||||||||||||||
| Linux | Linux | affected |
|
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Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Tue, 06 Oct 2026 09:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | IB/hfi1: Fix the PIO_CRED credit-return mmap | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-06T08:44:52.288Z
Reserved: 2026-09-25T10:25:14.326Z
Link: CVE-2026-98216
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-06T09:18:08.260
Modified: 2026-10-06T09:18:08.260
Link: CVE-2026-98216
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.