Bug 2436828 (CVE-2026-23085)

Summary:	CVE-2026-23085 kernel: irqchip/gic-v3-its: Avoid truncating memory addresses
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	Keywords:	Security
Target Milestone:	---
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Hardware:	All
OS:	Linux
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Doc Text:	An address truncation vulnerability was found in the Linux kernel's GICv3 ITS interrupt controller driver on 32-bit ARM systems with LPAE (Large Physical Address Extension). Physical addresses above 4GB are incorrectly stored in 32-bit unsigned long variables, causing address truncation. When kmalloc() returns memory from ZONE_NORMAL above 4GB, the truncated address causes the GICv3 driver to crash.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
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Description OSIDB Bzimport 2026-02-04 17:05:23 UTC

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

irqchip/gic-v3-its: Avoid truncating memory addresses

On 32-bit machines with CONFIG_ARM_LPAE, it is possible for lowmem
allocations to be backed by addresses physical memory above the 32-bit
address limit, as found while experimenting with larger VMSPLIT
configurations.

This caused the qemu virt model to crash in the GICv3 driver, which
allocates the 'itt' object using GFP_KERNEL. Since all memory below
the 4GB physical address limit is in ZONE_DMA in this configuration,
kmalloc() defaults to higher addresses for ZONE_NORMAL, and the
ITS driver stores the physical address in a 32-bit 'unsigned long'
variable.

Change the itt_addr variable to the correct phys_addr_t type instead,
along with all other variables in this driver that hold a physical
address.

The gicv5 driver correctly uses u64 variables, while all other irqchip
drivers don't call virt_to_phys or similar interfaces. It's expected that
other device drivers have similar issues, but fixing this one is
sufficient for booting a virtio based guest.

Comment 1 Jon Moroney 2026-02-04 19:28:03 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026020423-CVE-2026-23085-14e2@gregkh/T