CVE-2026-46276drm/amdgpu: fix zero-size GDS range init on RDNA4

Official description

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: fix zero-size GDS range init on RDNA4 RDNA4 (GFX 12) hardware removes the GDS, GWS, and OA on-chip memory resources. The gfx_v12_0 initialisation code correctly leaves adev->gds.gds_size, adev->gds.gws_size, and adev->gds.oa_size at zero to reflect this. amdgpu_ttm_init() unconditionally calls amdgpu_ttm_init_on_chip() for each of these resources regardless of size. When the size is zero, amdgpu_ttm_init_on_chip() forwards the call to ttm_range_man_init(), which calls drm_mm_init(mm, 0, 0). drm_mm_init() immediately fires DRM_MM_BUG_ON(start + size <= start) -- trivially true when size is zero -- crashing the kernel during modprobe of amdgpu on an RX 9070 XT. Guard against this by returning 0 early from amdgpu_ttm_init_on_chip() when size_in_page is zero. This skips TTM resource manager registration for hardware resources that are absent, without affecting any other GPU type. DRM_MM_BUG_ON() only asserts if CONFIG_DRM_DEBUG_MM is enabled in the kernel config. This is apparently rarely enabled as these chips have been in the market for over a year and this issue was only reported now. Oops-Analysis: http://oops.fenrus.org/reports/bugzilla.korg/221376/report.html (cherry picked from commit 5719ce5865279cad4fd5f01011fe037168503f2d)

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/1f5d33e7b0a9a2a140f46e22fb52eede323c5946
• https://git.kernel.org/stable/c/9bc925759c05feae7dfa9570e77131d54729c8ea
• https://git.kernel.org/stable/c/36f9602fb22ede69fcc8b422be0cf8105bf655ad
• https://git.kernel.org/stable/c/be0376affcafa0bbb371bb501579a825eae32281
• https://git.kernel.org/stable/c/0e21db1a77967bc15df662efdca8ea8a61d124ea
• https://git.kernel.org/stable/c/30c000a49094ec568c9b51b7421f7a4a3f0b0298
• https://git.kernel.org/stable/c/3e26c76891ab99fa173e9c501119fbb5c9f4600f
• https://git.kernel.org/stable/c/095a8b0ad3c3b5cdc3850d961adb8a8f735220bb