CVE-2025-68760

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

iommu/amd: Fix potential out-of-bounds read in iommummioshow

In iommummiowrite(), it validates the user-provided offset with the check: iommu->dbg_mmio_offset > iommu->mmio_phys_end - 4. This assumes a 4-byte access. However, the corresponding show handler, iommummioshow(), uses readq() to perform an 8-byte (64-bit) read.

If a user provides an offset equal to mmio_phys_end - 4, the check passes, and will lead to a 4-byte out-of-bounds read.

Fix this by adjusting the boundary check to use sizeof(u64), which corresponds to the size of the readq() operation.