Executive brief
A vulnerability in the Linux kernel's display driver for Samsung Exynos processors can cause a system crash or instability when a monitor's identification data (EDID) cannot be read. In such cases, the system attempts to use a default high-resolution display mode that the hardware cannot handle, leading to internal timing errors and system hangs. This primarily affects devices using Exynos4 series chips, such as certain mobile development boards.
Technical details
A vulnerability in the 'drm/exynos' HDMI driver occurs when EDID reading fails. In this scenario, the DRM core defaults to a 1024x768 resolution. However, certain hardware variants (specifically Exynos4 SoCs) cannot drive this mode, resulting in PLL steady-state failures and VSYNC timeouts. This triggers a kernel WARNING at 'drivers/gpu/drm/drm_atomic_helper.c' due to vblank wait timeouts, potentially leading to a denial-of-service (system hang). The fix involves explicitly reporting a safe 640x480 fallback mode when no modes are available from EDID.
Affected products
- Linux Linux Kernel Exynos4 SoCs; fixed in 6.9.0-rc5-next-20240424 and various stable branches
Timeline
- 2024-04-25: patched: Initial patch authored
- 2024-07-12: disclosed: CVE published
References
- https://git.kernel.org/stable/c/35bcf16b4a28c10923ff391d14f6ed0ae471ee5f
- https://git.kernel.org/stable/c/4dfffb50316c761c59386c9b002a10ac6d7bb6c9
- https://git.kernel.org/stable/c/510a6c0dfa6ec61d07a4b64698d8dc60045bd632
- https://git.kernel.org/stable/c/6d6bb258d886e124e5a5328e947b36fdcb3a6028
- https://git.kernel.org/stable/c/799d4b392417ed6889030a5b2335ccb6dcf030ab
- https://git.kernel.org/stable/c/c3ca24dfe9a2b3f4e8899af108829b0f4b4b15ec
- https://git.kernel.org/stable/c/e23f2eaf51ecb6ab4ceb770e747d50c1db2eb222