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CVE-2026-23266

fbdev: rivafb: fix divide error in nv3_arb() PUBLISHED

Description (CNA)

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 drivers/video/fbdev/riva/riva_hw.c:637 [inline] CalcStateExt+0x447/0x1b90 drivers/video/fbdev/riva/riva_hw.c:1246 riva_load_video_mode+0x8a9/0xea0 drivers/video/fbdev/riva/fbdev.c:779 rivafb_set_par+0xc0/0x5f0 drivers/video/fbdev/riva/fbdev.c:1196 fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1033 do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1188 __x64_sys_ioctl+0x122/0x190 fs/ioctl.c:856

Affected (CNA)

Vendor / productVersions
Linux / Linuxaffected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before ec5a58f4fd581875593ea92a65485e1906a53c0f; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 52916878db2b8e3769743a94484729f0844352df; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 526460a96c5443e2fc0fd231edd1f9c49d2de26b; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 78daf5984d96edec3b920c72a93bd6821b8710b7; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 9efa0dc46270a8723c158c64afbcf1dead72b28c; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 3e4cbd1d46c246dfa684c8e9d8c20ae0b960c50a; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 73f0391e92d404da68f7484e57c106c5e673dc7e; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 0209e21e3c372fa2da04c39214bec0b64e4eb5f4
Linux / Linuxaffected 2.6.12; unaffected 0 before 2.6.12; unaffected 5.10.251 through 5.10.*; unaffected 5.15.201 through 5.15.*; unaffected 6.1.164 through 6.1.*; unaffected 6.6.127 through 6.6.*; unaffected 6.12.74 through 6.12.*; unaffected 6.18.13 through 6.18.*; unaffected 6.19.3 through 6.19.*; unaffected 7.0 through *

CWE

No CWE identifiers supplied.

References