CVE-2021-47623

/// Technical description

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

powerpc/fixmap: Fix VM debug warning on unmap

Unmapping a fixmap entry is done by calling __set_fixmap()

with FIXMAP_PAGE_CLEAR as flags.

Today, powerpc __set_fixmap() calls map_kernel_page().

map_kernel_page() is not happy when called a second time

for the same page.

WARNING: CPU: 0 PID: 1 at arch/powerpc/mm/pgtable.c:194 set_pte_at+0xc/0x1e8

CPU: 0 PID: 1 Comm: swapper Not tainted 5.16.0-rc3-s3k-dev-01993-g350ff07feb7d-dirty #682

NIP: c0017cd4 LR: c00187f0 CTR: 00000010

REGS: e1011d50 TRAP: 0700 Not tainted (5.16.0-rc3-s3k-dev-01993-g350ff07feb7d-dirty)

MSR: 00029032 <EE,ME,IR,DR,RI> CR: 42000208 XER: 00000000

GPR00: c0165fec e1011e10 c14c0000 c0ee2550 ff800000 c0f3d000 00000000 c001686c

GPR08: 00001000 b00045a9 00000001 c0f58460 c0f50000 00000000 c0007e10 00000000

GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

GPR24: 00000000 00000000 c0ee2550 00000000 c0f57000 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