From: Thomas Zimmermann <tzimmermann@suse.de> mainline inclusion from mainline-v6.19-rc3 commit eb76d0f5553575599561010f24c277cc5b31d003 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/11645 CVE: CVE-2025-68296 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Protect vga_switcheroo_client_fb_set() with console lock. Avoids OOB access in fbcon_remap_all(). Without holding the console lock the call races with switching outputs. VGA switcheroo calls fbcon_remap_all() when switching clients. The fbcon function uses struct fb_info.node, which is set by register_framebuffer(). As the fb-helper code currently sets up VGA switcheroo before registering the framebuffer, the value of node is -1 and therefore not a legal value. For example, fbcon uses the value within set_con2fb_map() [1] as an index into an array. Moving vga_switcheroo_client_fb_set() after register_framebuffer() can result in VGA switching that does not switch fbcon correctly. Therefore move vga_switcheroo_client_fb_set() under fbcon_fb_registered(), which already holds the console lock. Fbdev calls fbcon_fb_registered() from within register_framebuffer(). Serializes the helper with VGA switcheroo's call to fbcon_remap_all(). Although vga_switcheroo_client_fb_set() takes an instance of struct fb_info as parameter, it really only needs the contained fbcon state. Moving the call to fbcon initialization is therefore cleaner than before. Only amdgpu, i915, nouveau and radeon support vga_switcheroo. For all other drivers, this change does nothing. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Link: https://elixir.bootlin.com/linux/v6.17/source/drivers/video/fbdev/core/fbcon... # [1] Fixes: 6a9ee8af344e ("vga_switcheroo: initial implementation (v15)") Acked-by: Javier Martinez Canillas <javierm@redhat.com> Acked-by: Alex Deucher <alexander.deucher@amd.com> Cc: dri-devel@lists.freedesktop.org Cc: nouveau@lists.freedesktop.org Cc: amd-gfx@lists.freedesktop.org Cc: linux-fbdev@vger.kernel.org Cc: <stable@vger.kernel.org> # v2.6.34+ Link: https://patch.msgid.link/20251105161549.98836-1-tzimmermann@suse.de Conflicts: drivers/gpu/drm/drm_fb_helper.c drivers/video/fbdev/core/fbcon.c [Context differences.] Signed-off-by: Xia Fukun <xiafukun@huawei.com> --- drivers/gpu/drm/drm_fb_helper.c | 14 -------------- drivers/video/fbdev/core/fbcon.c | 9 +++++++++ 2 files changed, 9 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index eee7b56d441f..9691c93f19a0 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -30,9 +30,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/console.h> -#include <linux/pci.h> #include <linux/sysrq.h> -#include <linux/vga_switcheroo.h> #include <drm/drm_atomic.h> #include <drm/drm_drv.h> @@ -575,11 +573,6 @@ EXPORT_SYMBOL(drm_fb_helper_release_info); */ void drm_fb_helper_unregister_info(struct drm_fb_helper *fb_helper) { - struct fb_info *info = fb_helper->info; - struct device *dev = info->device; - - if (dev_is_pci(dev)) - vga_switcheroo_client_fb_set(to_pci_dev(dev), NULL); unregister_framebuffer(fb_helper->info); } EXPORT_SYMBOL(drm_fb_helper_unregister_info); @@ -1673,7 +1666,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper) { struct drm_client_dev *client = &fb_helper->client; struct drm_fb_helper_surface_size sizes; - struct fb_info *info; int ret; ret = drm_fb_helper_find_sizes(fb_helper, &sizes); @@ -1691,12 +1683,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper) strcpy(fb_helper->fb->comm, "[fbcon]"); - info = fb_helper->info; - - /* Set the fb info for vgaswitcheroo clients. Does nothing otherwise. */ - if (dev_is_pci(info->device)) - vga_switcheroo_client_fb_set(to_pci_dev(info->device), info); - return 0; } diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index cc3302afae78..e0696859c6ab 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -64,6 +64,7 @@ #include <linux/console.h> #include <linux/string.h> #include <linux/kd.h> +#include <linux/pci.h> #include <linux/slab.h> #include <linux/fb.h> #include <linux/fbcon.h> @@ -75,6 +76,7 @@ #include <linux/interrupt.h> #include <linux/crc32.h> /* For counting font checksums */ #include <linux/uaccess.h> +#include <linux/vga_switcheroo.h> #include <asm/irq.h> #include "fbcon.h" @@ -2885,6 +2887,9 @@ void fbcon_fb_unregistered(struct fb_info *info) console_lock(); + if (info->device && dev_is_pci(info->device)) + vga_switcheroo_client_fb_set(to_pci_dev(info->device), NULL); + fbcon_registered_fb[info->node] = NULL; fbcon_num_registered_fb--; @@ -3018,6 +3023,10 @@ static int do_fb_registered(struct fb_info *info) } } + /* Set the fb info for vga_switcheroo clients. Does nothing otherwise. */ + if (info->device && dev_is_pci(info->device)) + vga_switcheroo_client_fb_set(to_pci_dev(info->device), info); + return ret; } -- 2.34.1