CVE-2024-42293

/// Technical description

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

arm64: mm: Fix lockless walks with static and dynamic page-table folding

Lina reports random oopsen originating from the fast GUP code when

16K pages are used with 4-level page-tables, the fourth level being

folded at runtime due to lack of LPA2.

In this configuration, the generic implementation of

p4d_offset_lockless() will return a 'p4d_t *' corresponding to the

'pgd_t' allocated on the stack of the caller, gup_fast_pgd_range().

This is normally fine, but when the fourth level of page-table is folded

at runtime, pud_offset_lockless() will offset from the address of the

'p4d_t' to calculate the address of the PUD in the same page-table page.

This results in a stray stack read when the 'p4d_t' has been allocated

on the stack and can send the walker into the weeds.

Fix the problem by providing our own definition of p4d_offset_lockless()

when CONFIG_PGTABLE_LEVELS <= 4 which returns the real page-table

pointer rather

/// 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