From fcb74da1eb8edd3a4ef9b9724f88ed709d684227 Mon Sep 17 00:00:00 2001 From: Emil Lundmark Date: Mon, 28 May 2018 16:27:11 +0200 Subject: [PATCH] drm: udl: Destroy framebuffer only if it was initialized MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This fixes a NULL pointer dereference that can happen if the UDL driver is unloaded before the framebuffer is initialized. This can happen e.g. if the USB device is unplugged right after it was plugged in. As explained by Stéphane Marchesin: It happens when fbdev is disabled (which is the case for Chrome OS). Even though intialization of the fbdev part is optional (it's done in udlfb_create which is the callback for fb_probe()), the teardown isn't optional (udl_driver_unload -> udl_fbdev_cleanup -> udl_fbdev_destroy). Note that udl_fbdev_cleanup *tries* to be conditional (you can see it does if (!udl->fbdev)) but that doesn't work, because udl->fbdev is always set during udl_fbdev_init. Cc: stable@vger.kernel.org Suggested-by: Sean Paul Reviewed-by: Sean Paul Acked-by: Daniel Vetter Signed-off-by: Emil Lundmark Signed-off-by: Sean Paul Link: https://patchwork.freedesktop.org/patch/msgid/20180528142711.142466-1-lndmrk@chromium.org Signed-off-by: Sean Paul --- drivers/gpu/drm/udl/udl_fb.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/udl/udl_fb.c b/drivers/gpu/drm/udl/udl_fb.c index dbb62f6eb48a..dd9ffded223b 100644 --- a/drivers/gpu/drm/udl/udl_fb.c +++ b/drivers/gpu/drm/udl/udl_fb.c @@ -432,9 +432,11 @@ static void udl_fbdev_destroy(struct drm_device *dev, { drm_fb_helper_unregister_fbi(&ufbdev->helper); drm_fb_helper_fini(&ufbdev->helper); - drm_framebuffer_unregister_private(&ufbdev->ufb.base); - drm_framebuffer_cleanup(&ufbdev->ufb.base); - drm_gem_object_put_unlocked(&ufbdev->ufb.obj->base); + if (ufbdev->ufb.obj) { + drm_framebuffer_unregister_private(&ufbdev->ufb.base); + drm_framebuffer_cleanup(&ufbdev->ufb.base); + drm_gem_object_put_unlocked(&ufbdev->ufb.obj->base); + } } int udl_fbdev_init(struct drm_device *dev) -- 2.30.2