CVE-2024-49878

/// Technical description

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

resource: fix region_intersects() vs add_memory_driver_managed()

On a system with CXL memory, the resource tree (/proc/iomem) related to

CXL memory may look like something as follows.

490000000-50fffffff : CXL Window 0

490000000-50fffffff : region0

490000000-50fffffff : dax0.0

490000000-50fffffff : System RAM (kmem)

Because drivers/dax/kmem.c calls add_memory_driver_managed() during

onlining CXL memory, which makes "System RAM (kmem)" a descendant of "CXL

Window X". This confuses region_intersects(), which expects all "System

RAM" resources to be at the top level of iomem_resource. This can lead to

bugs.

For example, when the following command line is executed to write some

memory in CXL memory range via /dev/mem,

$ dd if=data of=/dev/mem bs=$((1 << 10)) seek=$((0x490000000 >> 10)) count=1

dd: error writing '/dev/mem': Bad address

1+0 records in

0+0 records out

0 bytes copied, 0.0283507 s, 0.0

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References