CVE-2022-49081

/// Technical description

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

highmem: fix checks in __kmap_local_sched_{in,out}

When CONFIG_DEBUG_KMAP_LOCAL is enabled __kmap_local_sched_{in,out} check

that even slots in the tsk->kmap_ctrl.pteval are unmapped. The slots are

initialized with 0 value, but the check is done with pte_none. 0 pte

however does not necessarily mean that pte_none will return true. e.g.

on xtensa it returns false, resulting in the following runtime warnings:

WARNING: CPU: 0 PID: 101 at mm/highmem.c:627 __kmap_local_sched_out+0x51/0x108

CPU: 0 PID: 101 Comm: touch Not tainted 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13

Call Trace:

dump_stack+0xc/0x40

__warn+0x8f/0x174

warn_slowpath_fmt+0x48/0xac

__kmap_local_sched_out+0x51/0x108

__schedule+0x71a/0x9c4

preempt_schedule_irq+0xa0/0xe0

common_exception_return+0x5c/0x93

do_wp_page+0x30e/0x330

handle_mm_fault+0xa70/0xc3c

do_page_fault+0x1d8/0x3c4

common_exception+0x7f/0x7f

WARNING: CPU:

/// 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