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

drm/panthor: Be stricter about IO mapping flags

The current panthor_device_mmap_io() implementation has two issues:

1. For mapping DRM_PANTHOR_USER_FLUSH_ID_MMIO_OFFSET,
panthor_device_mmap_io() bails if VM_WRITE is set, but does not clear
VM_MAYWRITE. That means userspace can use mprotect() to make the mapping
writable later on. This is a classic Linux driver gotcha.
I don't think this actually has any impact in practice:
When the GPU is powered, writes to the FLUSH_ID seem to be ignored; and
when the GPU is not powered, the dummy_latest_flush page provided by the
driver is deliberately designed to not do any flushes, so the only thing
writing to the dummy_latest_flush could achieve would be to make *more*
flushes happen.

2. panthor_device_mmap_io() does not block MAP_PRIVATE mappings (which are
mappings without the VM_SHARED flag).
MAP_PRIVATE in combination with VM_MAYWRITE indicates that the VMA has
copy-on-write semantics, which for VM_PFNMAP are semi-supported but
fairly cursed.
In particular, in such a mapping, the driver can only install PTEs
during mmap() by calling remap_pfn_range() (because remap_pfn_range()
wants to **store the physical address of the mapped physical memory into
the vm_pgoff of the VMA**); installing PTEs later on with a fault
handler (as panthor does) is not supported in private mappings, and so
if you try to fault in such a mapping, vmf_insert_pfn_prot() splats when
it hits a BUG() check.

Fix it by clearing the VM_MAYWRITE flag (userspace writing to the FLUSH_ID
doesn't make sense) and requiring VM_SHARED (copy-on-write semantics for
the FLUSH_ID don't make sense).

Reproducers for both scenarios are in the notes of my patch on the mailing
list; I tested that these bugs exist on a Rock 5B machine.

Note that I only compile-tested the patch, I haven't tested it; I don't
have a working kernel build setup for the test machine yet. Please test it
before applying it.
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Thu, 13 Feb 2025 00:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-285

Tue, 26 Nov 2024 22:45:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.12:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.12:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.12:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.12:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.12:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.12:rc6:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel

Fri, 22 Nov 2024 14:00:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate


Tue, 19 Nov 2024 17:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: drm/panthor: Be stricter about IO mapping flags The current panthor_device_mmap_io() implementation has two issues: 1. For mapping DRM_PANTHOR_USER_FLUSH_ID_MMIO_OFFSET, panthor_device_mmap_io() bails if VM_WRITE is set, but does not clear VM_MAYWRITE. That means userspace can use mprotect() to make the mapping writable later on. This is a classic Linux driver gotcha. I don't think this actually has any impact in practice: When the GPU is powered, writes to the FLUSH_ID seem to be ignored; and when the GPU is not powered, the dummy_latest_flush page provided by the driver is deliberately designed to not do any flushes, so the only thing writing to the dummy_latest_flush could achieve would be to make *more* flushes happen. 2. panthor_device_mmap_io() does not block MAP_PRIVATE mappings (which are mappings without the VM_SHARED flag). MAP_PRIVATE in combination with VM_MAYWRITE indicates that the VMA has copy-on-write semantics, which for VM_PFNMAP are semi-supported but fairly cursed. In particular, in such a mapping, the driver can only install PTEs during mmap() by calling remap_pfn_range() (because remap_pfn_range() wants to **store the physical address of the mapped physical memory into the vm_pgoff of the VMA**); installing PTEs later on with a fault handler (as panthor does) is not supported in private mappings, and so if you try to fault in such a mapping, vmf_insert_pfn_prot() splats when it hits a BUG() check. Fix it by clearing the VM_MAYWRITE flag (userspace writing to the FLUSH_ID doesn't make sense) and requiring VM_SHARED (copy-on-write semantics for the FLUSH_ID don't make sense). Reproducers for both scenarios are in the notes of my patch on the mailing list; I tested that these bugs exist on a Rock 5B machine. Note that I only compile-tested the patch, I haven't tested it; I don't have a working kernel build setup for the test machine yet. Please test it before applying it.
Title drm/panthor: Be stricter about IO mapping flags
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-05-04T09:52:13.347Z

Reserved: 2024-11-19T17:17:24.976Z

Link: CVE-2024-53071

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Analyzed

Published: 2024-11-19T18:15:26.793

Modified: 2024-11-26T22:18:28.540

Link: CVE-2024-53071

cve-icon Redhat

Severity : Moderate

Publid Date: 2024-11-19T00:00:00Z

Links: CVE-2024-53071 - Bugzilla

cve-icon OpenCVE Enrichment

No data.