CVE-2026-23266 — fbdev: rivafb: fix divide error in nv3_arb()

Affected: Linux

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

fbdev: rivafb: fix divide error in nv3_arb()

A userspace program can trigger the RIVA NV3 arbitration code by calling the FBIOPUT_VSCREENINFO ioctl on /dev/fb*. When doing so, the driver recomputes FIFO arbitration parameters in nv3_arb(), using state->mclk_khz (derived from the PRAMDAC MCLK PLL) as a divisor without validating it first.

In a normal setup, state->mclk_khz is provided by the real hardware and is non-zero. However, an attacker can construct a malicious or misconfigured device (e.g. a crafted/emulated PCI device) that exposes a bogus PLL configuration, causing state->mclk_khz to become zero. Once nv3_get_param() calls nv3_arb(), the division by state->mclk_khz in the gns calculation causes a divide error and crashes the kernel.

Fix this by checking whether state->mclk_khz is zero and bailing out before doing the division.

The following log reveals it:

rivafb: setting virtual Y resolution to 2184 divide error: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 0 PID: 2187 Comm: syz-executor.0 Not tainted 5.18.0-rc1+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 RIP: 0010:nv3_arb drivers/video/fbdev/riva/riva_hw.c:439 [inline] RIP: 0010:nv3_get_param+0x3ab/0x13b0 drivers/video/fbdev/riva/riva_hw.c:546 Call Trace: nv3CalcArbitration.constprop.0+0x255/0x460 drivers/video/fbdev/riva/riva_hw.c:603 nv3UpdateArbitrationSettings driv…

USN-8492-1 — linux, linux-aws, linux-aws-fips, linux-gcp, linux-gcp-fips, linux-ibm, linux-nvidia, linux-nvidia-6.8, linux-oracle, l…

Affected: Ubuntu:22.04:LTS: linux-nvidia-6.8, Ubuntu:Pro:Realtime:22.04:LTS: linux-realtime-6.8, Ubuntu:24.04:LTS: linux, Ubuntu:24.04:LTS: linux-aws, Ubuntu:24.04:LTS: linux-gcp, Ubuntu:24.04:LTS: linux-ibm, Ubuntu:24.04:LTS: linux-nvidia, Ubuntu:24.04:LTS: linux-oracle, Ubuntu:Pro:Realtime:24.04:LTS: linux-realtime, Ubuntu:Pro:FIPS-updates:24.04:LTS: linux-aws-fips and 1 more

Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system. This update corrects flaws in the following subsystems: - ARM64 architecture; - MIPS architecture; - PowerPC architecture; - x86 architecture; - Block layer subsystem; - Cryptographic API; - ACPI drivers; - ATM drivers; - RNBD block device driver; - Ublk userspace block driver; - Bus devices; - Character device driver; - TPM device driver; - Clock framework and drivers; - Clocksource drivers; - CPU idle management framework; - Hardware crypto device drivers; - DMA engine subsystem; - EFI core; - GPIO subsystem; - GPU drivers; - HID subsystem; - Hardware monitoring drivers; - IIO subsystem; - InfiniBand drivers; - IOMMU subsystem; - Multiple devices driver; - Media drivers; - Multifunction device drivers; - Broadcom VK accelerator driver; - MOST (Media Oriented Systems Transport) drivers; - MTD block device drivers; - Ethernet bonding driver; - Network drivers; - Mellanox network drivers; - STMicroelectronics network drivers; - NTB driver; - NVME drivers; - PCI subsystem; - Performance monitor drivers; - Pin controllers subsystem; - x86 platform drivers; - Power supply drivers; - RapidIO drivers; - RAS (Reliability, Availability, Serviceability) subsystem; - Remote Processor subsystem; - RPMSG subsystem; - S/390 drivers; - SCSI subsystem; - MediaTek SoC dr…

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CVE-2026-23266 — fbdev: rivafb: fix divide error in nv3_arb()

USN-8492-1 — linux, linux-aws, linux-aws-fips, linux-gcp, linux-gcp-fips, linux-ibm, linux-nvidia, linux-nvidia-6.8, linux-oracle, l…