CVE-2026-23266

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> fbdev: rivafb: fix divide error in nv3_arb()<br /> <br /> A userspace program can trigger the RIVA NV3 arbitration code by calling<br /> the FBIOPUT_VSCREENINFO ioctl on /dev/fb*. When doing so, the driver<br /> recomputes FIFO arbitration parameters in nv3_arb(), using state-&gt;mclk_khz<br /> (derived from the PRAMDAC MCLK PLL) as a divisor without validating it<br /> first.<br /> <br /> In a normal setup, state-&gt;mclk_khz is provided by the real hardware and is<br /> non-zero. However, an attacker can construct a malicious or misconfigured<br /> device (e.g. a crafted/emulated PCI device) that exposes a bogus PLL<br /> configuration, causing state-&gt;mclk_khz to become zero. Once<br /> nv3_get_param() calls nv3_arb(), the division by state-&gt;mclk_khz in the gns<br /> calculation causes a divide error and crashes the kernel.<br /> <br /> Fix this by checking whether state-&gt;mclk_khz is zero and bailing out before<br /> doing the division.<br /> <br /> The following log reveals it:<br /> <br /> rivafb: setting virtual Y resolution to 2184<br /> divide error: 0000 [#1] PREEMPT SMP KASAN PTI<br /> CPU: 0 PID: 2187 Comm: syz-executor.0 Not tainted 5.18.0-rc1+ #1<br /> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014<br /> RIP: 0010:nv3_arb drivers/video/fbdev/riva/riva_hw.c:439 [inline]<br /> RIP: 0010:nv3_get_param+0x3ab/0x13b0 drivers/video/fbdev/riva/riva_hw.c:546<br /> Call Trace:<br /> nv3CalcArbitration.constprop.0+0x255/0x460 drivers/video/fbdev/riva/riva_hw.c:603<br /> nv3UpdateArbitrationSettings drivers/video/fbdev/riva/riva_hw.c:637 [inline]<br /> CalcStateExt+0x447/0x1b90 drivers/video/fbdev/riva/riva_hw.c:1246<br /> riva_load_video_mode+0x8a9/0xea0 drivers/video/fbdev/riva/fbdev.c:779<br /> rivafb_set_par+0xc0/0x5f0 drivers/video/fbdev/riva/fbdev.c:1196<br /> fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1033<br /> do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1109<br /> fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1188<br /> __x64_sys_ioctl+0x122/0x190 fs/ioctl.c:856