From 1b99b72489c6a2d9fb3156b403510dc5f6c8b6a5 Mon Sep 17 00:00:00 2001 From: Stefan Christ Date: Mon, 14 Nov 2016 00:03:11 +0100 Subject: [PATCH] drm/fb-helper: fix segfaults in drm_fb_helper_debug_* A drm driver that is implementing fb_debug_enter and fb_debug_leave in struct fb_ops with drm fb helper functions drm_fb_helper_debug_enter and drm_fb_helper_debug_leave must also implement the callback 'mode_set_base_atomic' in struct drm_crtc_helper_funcs. See Documentation/DocBook/kgdb.tmpl. The current implementation will segfault when 'mode_set_base_atomic' is a NULL pointer. Before this patch at least the drm drivers armada, ast, qxl, udl and virtio do not have a 'mode_set_base_atomic' implementation but using drm_fb_helper_debug_(enter|leave). So these drivers may segfault when callbacks fb_debug_(enter|leave) are called. Avoid the issue by just checking for NULL pointers. So all drivers can unconditionally implement fb_debug_(enter|leave) with the drm_fb_helper functions. If callback 'mode_set_base_atomic' is not implemented, the code in drm_fb_helper_debug_(enter|leave) does effectively nothing. Signed-off-by: Stefan Christ Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/1479078208-25221-2-git-send-email-contact@stefanchrist.eu --- drivers/gpu/drm/drm_fb_helper.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 36797c465edc..14547817566d 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -256,6 +256,9 @@ int drm_fb_helper_debug_enter(struct fb_info *info) continue; funcs = mode_set->crtc->helper_private; + if (funcs->mode_set_base_atomic == NULL) + continue; + drm_fb_helper_save_lut_atomic(mode_set->crtc, helper); funcs->mode_set_base_atomic(mode_set->crtc, mode_set->fb, @@ -309,6 +312,9 @@ int drm_fb_helper_debug_leave(struct fb_info *info) continue; } + if (funcs->mode_set_base_atomic == NULL) + continue; + drm_fb_helper_restore_lut_atomic(mode_set->crtc); funcs->mode_set_base_atomic(mode_set->crtc, fb, crtc->x, crtc->y, LEAVE_ATOMIC_MODE_SET); -- 2.20.1