Commit 615cc422 authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

drm/vesadrm: Avoid NULL-ptr deref in vesadrm_pmi_cmap_write() 



Only set PMI fields if the screen_info's Vesa PM segment has been
set. Vesa PMI is the power-management interface. It also provides
means to set the color palette. The interface is optional, so not
all VESA graphics cards support it. Print vesafb's warning [1] if
the hardware palette cannot be set at all.

If unsupported the field PrimaryPalette in struct vesadrm.pmi is
NULL, which results in a segmentation fault. Happens with qemu's
Cirrus emulation.

Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Fixes: 814d270b ("drm/sysfb: vesadrm: Add gamma correction")
Link: https://elixir.bootlin.com/linux/v6.15/source/drivers/video/fbdev/vesafb.c#L375

 # 1
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Acked-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250617140944.142392-1-tzimmermann@suse.de
parent f6faebc1

drivers/gpu/drm/sysfb/vesadrm.c

+9 −4
Original line number Diff line number Diff line
@@ -362,14 +362,19 @@ static struct vesadrm_device *vesadrm_device_create(struct drm_driver *drv, 


	if (!__screen_info_vbe_mode_nonvga(si)) {

		vesa->cmap_write = vesadrm_vga_cmap_write;

#if defined(CONFIG_X86_32)

	} else {

#if defined(CONFIG_X86_32)

		phys_addr_t pmi_base = __screen_info_vesapm_info_base(si);



		if (pmi_base) {

			const u16 *pmi_addr = phys_to_virt(pmi_base);



			vesa->pmi.PrimaryPalette = (u8 *)pmi_addr + pmi_addr[2];

			vesa->cmap_write = vesadrm_pmi_cmap_write;

		} else

#endif

		if (format->is_color_indexed)

			drm_warn(dev, "hardware palette is unchangeable, colors may be incorrect\n");

	}



#ifdef CONFIG_X86