Bug 2451233 (CVE-2026-23345)
| Summary: | CVE-2026-23345 kernel: arm64: gcs: Do not set PTE_SHARED on GCS mappings if FEAT_LPA2 is enabled | ||
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| Product: | [Other] Security Response | Reporter: | OSIDB Bzimport <bzimport> |
| Component: | vulnerability | Assignee: | Product Security <prodsec-ir-bot> |
| Status: | NEW --- | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | unspecified | Keywords: | Security |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | --- | |
| Doc Text: |
A flaw was found in the Linux kernel. When the FEAT_LPA2 feature is enabled on ARM64 systems, the kernel incorrectly handles the PTE_SHARED bits in Graphics Control System (GCS) memory mappings. This misconfiguration can lead to a kernel paging request and subsequently a system panic, resulting in a Denial of Service (DoS). A local user or specific system configuration could trigger this vulnerability.
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Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | Type: | --- | |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
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.