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.
Metrics
Affected Vendors & Products
References
History
Tue, 26 Nov 2024 22:45:00 +0000
Type | Values Removed | Values Added |
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First Time appeared |
Linux
Linux linux Kernel |
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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 |
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References |
| |
Metrics |
threat_severity
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cvssV3_1
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Tue, 19 Nov 2024 17:30:00 +0000
Type | Values Removed | Values Added |
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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 |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2024-11-19T17:22:38.327Z
Updated: 2024-12-19T09:38:26.990Z
Reserved: 2024-11-19T17:17:24.976Z
Link: CVE-2024-53071
Vulnrichment
No data.
NVD
Status : Analyzed
Published: 2024-11-19T18:15:26.793
Modified: 2024-11-26T22:18:28.540
Link: CVE-2024-53071
Redhat