CVE-2026-23345

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

arm64: gcs: Do not set PTE_SHARED on GCS mappings if FEAT_LPA2 is enabled

When FEAT_LPA2 is enabled, bits 8-9 of the PTE replace the

shareability attribute with bits 50-51 of the output address. The

_PAGE_GCS{,_RO} definitions include the PTE_SHARED bits as 0b11 (this

matches the other _PAGE_* definitions) but using this macro directly

leads to the following panic when enabling GCS on a system/model with

LPA2:

Unable to handle kernel paging request at virtual address fffff1ffc32d8008

Mem abort info:

ESR = 0x0000000096000004

EC = 0x25: DABT (current EL), IL = 32 bits

SET = 0, FnV = 0

EA = 0, S1PTW = 0

FSC = 0x04: level 0 translation fault

Data abort info:

ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000

CM = 0, WnR = 0, TnD = 0, TagAccess = 0

GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0

swapper pgtable: 4k pages, 52-bit VAs, pgdp=0000000060f4d000

[fffff1ffc32d8008] pgd=100000006184b003, p4d=0000000000000000

Internal error: Oops: 0000000096000004 [#1] SMP

CPU: 0 UID: 0 PID: 513 Comm: gcs_write_fault Tainted: G M 7.0.0-rc1 #1 PREEMPT

Tainted: [M]=MACHINE_CHECK

Hardware name: QEMU QEMU Virtual Machine, BIOS 2025.02-8+deb13u1 11/08/2025

pstate: 03402005 (nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)

pc : zap_huge_pmd+0x168/0x468

lr : zap_huge_pmd+0x2c/0x468

sp : ffff800080beb660

x29: ffff800080beb660 x28: fff00000c2058180 x27: ffff800080beb898

x26: fff00000c2058180 x25: ffff800080beb820 x24: 00c800010b600f41

x23: ffffc1ffc30af1a8 x22: fff00000c2058180 x21: 0000ffff8dc00000

x20: fff00000c2bc6370 x19: ffff800080beb898 x18: ffff800080bebb60

x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000007

x14: 000000000000000a x13: 0000aaaacbbbffff x12: 0000000000000000

x11: 0000ffff8ddfffff x10: 00000000000001fe x9 : 0000ffff8ddfffff

x8 : 0000ffff8de00000 x7 : 0000ffff8da00000 x6 : fff00000c2bc6370

x5 : 0000ffff8da00000 x4 : 000000010b600000 x3 : ffffc1ffc0000000

x2 : fff00000c2058180 x1 : fffff1ffc32d8000 x0 : 000000c00010b600

Call trace:

zap_huge_pmd+0x168/0x468 (P)

unmap_page_range+0xd70/0x1560

unmap_single_vma+0x48/0x80

unmap_vmas+0x90/0x180

unmap_region+0x88/0xe4

vms_complete_munmap_vmas+0xf8/0x1e0

do_vmi_align_munmap+0x158/0x180

do_vmi_munmap+0xac/0x160

__vm_munmap+0xb0/0x138

vm_munmap+0x14/0x20

gcs_free+0x70/0x80

mm_release+0x1c/0xc8

exit_mm_release+0x28/0x38

do_exit+0x190/0x8ec

do_group_exit+0x34/0x90

get_signal+0x794/0x858

arch_do_signal_or_restart+0x11c/0x3e0

exit_to_user_mode_loop+0x10c/0x17c

el0_da+0x8c/0x9c

el0t_64_sync_handler+0xd0/0xf0

el0t_64_sync+0x198/0x19c

Code: aa1603e2 d34cfc00 cb813001 8b011861 (f9400420)

Similarly to how the kernel handles protection_map[], use a

gcs_page_prot variable to store the protection bits and clear PTE_SHARED

if LPA2 is enabled.

Also remove the unused PAGE_GCS{,_RO} macros.