Description
In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Clear Present bit before tearing down copied context entry copied_context_tear_down() zeroes the 128-bit context entry with context_clear_entry() while the Present bit is still set, and only then issues the context-cache and IOTLB invalidations. This leaves a window in which hardware can fetch a torn entry, with some fields already zeroed while Present is still set, leading to unpredictable behaviour or spurious faults. While x86 provides strong write ordering, the compiler may reorder the writes to the two 64-bit halves of the entry, and the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes. There is no cacheline flush before the invalidation either, so on an IOMMU without coherent access to the context table the zeroed entry may not be visible to hardware at the point the invalidation is submitted. Apply the same ownership handshake described in the VT-d spec, Section 6.5.3.3 ("Guidance to Software for Invalidations"): clear only the Present bit, flush it out to the IOMMU, perform the invalidations, and only then zero the remainder of the entry.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
c7191984e5aade540f1a3845a116537c89572655 to < 97750a8dce79c1a9b2b2d2a020b61b800141996caffectedc7191984e5aade540f1a3845a116537c89572655 to < 3c88cfedc7768b1ae2dc7ddc71547ae9a1aaff7daffectedc7191984e5aade540f1a3845a116537c89572655 to < 6b822d18c33af9d1e16a8e5e6aa6e656987b09deaffectedc7191984e5aade540f1a3845a116537c89572655 to < f532c57985b1a7d6b7e37e05506b46d413e5cca4affected
Linux Linux
Default version status: affected
6.12affected0 to < 6.12unaffected6.12.110 to ≤ 6.12.*unaffected6.18.52 to ≤ 6.18.*unaffected7.2.6 to ≤ 7.2.*unaffected7.3 to ≤ *unaffected