CVE-2026-64186iommu/amd: Remove latent out-of-bounds access in IOMMU debugfs

Official description

In the Linux kernel, the following vulnerability has been resolved: iommu/amd: Remove latent out-of-bounds access in IOMMU debugfs In iommu_mmio_write() and iommu_capability_write(), the variables dbg_mmio_offset and dbg_cap_offset are declared as int. However, they are populated using kstrtou32_from_user(). If a user provides a sufficiently large value, it can become a negative integer. Prior to this patch, the AMD IOMMU debugfs implementation was already protected by different mechanisms. 1. #define OFS_IN_SZ 8 ensures the user string <= 8 bytes, so e.g. 0xffffffff isn't a valid input. if (cnt > OFS_IN_SZ) return -EINVAL; 2. Implicit type promotion in iommu_mmio_write(), dbg_mmio_offset is int and iommu->mmio_phys_end is u64 if (dbg_mmio_offset > iommu->mmio_phys_end - sizeof(u64)) return -EINVAL; 3. The show handlers would currently catch the negative number and refuse to perform the read. Replace kstrtou32_from_user() with kstrtos32_from_user() to parse the input, and check for negative values to explicitly prevent out-of-bounds memory accesses directly in iommu_mmio_write() and iommu_capability_write().

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/488d2c76bd9f78433a70690d1054bfae3d39a407
• https://git.kernel.org/stable/c/62f9dfbf1aceae88b03c5ca08f7d36e943939dec
• https://git.kernel.org/stable/c/8dfd3d8d74435344ee8dc9237596959c8b2a6cbe