CVE-2024-46847

/// Technical description

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

mm: vmalloc: ensure vmap_block is initialised before adding to queue

Commit 8c61291fd850 ("mm: fix incorrect vbq reference in

purge_fragmented_block") extended the 'vmap_block' structure to contain a

'cpu' field which is set at allocation time to the id of the initialising

CPU.

When a new 'vmap_block' is being instantiated by new_vmap_block(), the

partially initialised structure is added to the local 'vmap_block_queue'

xarray before the 'cpu' field has been initialised. If another CPU is

concurrently walking the xarray (e.g. via vm_unmap_aliases()), then it

may perform an out-of-bounds access to the remote queue thanks to an

uninitialised index.

This has been observed as UBSAN errors in Android:

| Internal error: UBSAN: array index out of bounds: 00000000f2005512 [#1] PREEMPT SMP

|

| Call trace:

| purge_fragmented_block+0x204/0x21c

| _vm_unmap_aliases+0x170/0x378

| vm_unmap_aliases+0x1c/0x28

| change_

/// 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