From: Tvrtko Ursulin Date: Tue, 30 Jun 2015 09:06:27 +0000 (+0100) Subject: drm/i915: Fix failure paths around initial fbdev allocation X-Git-Tag: v4.5-rc1~74^2~37^2~140 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=51f1385b90c1ad30896bd62b1ff97aa4edb1a163;p=linux.git drm/i915: Fix failure paths around initial fbdev allocation We had two failure modes here: 1. Deadlock in intelfb_alloc failure path where it calls drm_framebuffer_remove, which grabs the struct mutex and intelfb_create (caller of intelfb_alloc) was already holding it. 2. Deadlock in intelfb_create failure path where it calls drm_framebuffer_unreference, which grabs the struct mutex and intelfb_create was already holding it. [Daniel Vetter on why struct_mutex needs to be locked in the second half of intelfb_create: "The vma [for the fbdev] is pinned, the problem is that we re-lookup it a few times, which is racy. We should instead track the vma directly, but oh well we don't."] v2: * Reformat commit msg to 72 chars. (Lukas Wunner) * Add third failure mode. (Lukas Wunner) v5: * Rebase on drm-intel-nightly 2015y-09m-01d-09h-06m-08s UTC, rephrase commit message. (Jani Nicula) v6: * In intelfb_alloc, if __intel_framebuffer_create failed, fb will be an ERR_PTR, thus not null. So in the failure path we need to check for IS_ERR_OR_NULL to avoid calling drm_framebuffer_remove on the ERR_PTR. (Lukas Wunner) * Since this is init code a drm_framebuffer_unreference should be all we need. drm_framebuffer_remove is for framebuffers that userspace has created - and is getting somewhat defeatured. (Daniel Vetter) v7: * Clarify why struct_mutex needs to be locked in the second half of intelfb_create. (Daniel Vetter) Fixes: 60a5ca015ffd ("drm/i915: Add locking around framebuffer_references--") Reported-by: Lukas Wunner Signed-off-by: Tvrtko Ursulin [Lukas: Create v3 + v4 + v5 + v6 + v7 based on Tvrtko's v2] Signed-off-by: Lukas Wunner Cc: Chris Wilson Cc: Ville Syrjälä Reviewed-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/47d4e88c91b3bf0f7a280cabec54c8c8cf0cf6f2.1446892879.git.lukas@wunner.de Signed-off-by: Jani Nikula --- diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c index 2240e709ede6..db82ad45de13 100644 --- a/drivers/gpu/drm/i915/intel_fbdev.c +++ b/drivers/gpu/drm/i915/intel_fbdev.c @@ -119,7 +119,7 @@ static int intelfb_alloc(struct drm_fb_helper *helper, { struct intel_fbdev *ifbdev = container_of(helper, struct intel_fbdev, helper); - struct drm_framebuffer *fb; + struct drm_framebuffer *fb = NULL; struct drm_device *dev = helper->dev; struct drm_i915_private *dev_priv = to_i915(dev); struct drm_mode_fb_cmd2 mode_cmd = {}; @@ -138,6 +138,8 @@ static int intelfb_alloc(struct drm_fb_helper *helper, mode_cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth); + mutex_lock(&dev->struct_mutex); + size = mode_cmd.pitches[0] * mode_cmd.height; size = PAGE_ALIGN(size); @@ -165,16 +167,19 @@ static int intelfb_alloc(struct drm_fb_helper *helper, ret = intel_pin_and_fence_fb_obj(NULL, fb, NULL); if (ret) { DRM_ERROR("failed to pin obj: %d\n", ret); - goto out_fb; + goto out; } + mutex_unlock(&dev->struct_mutex); + ifbdev->fb = to_intel_framebuffer(fb); return 0; -out_fb: - drm_framebuffer_remove(fb); out: + mutex_unlock(&dev->struct_mutex); + if (!IS_ERR_OR_NULL(fb)) + drm_framebuffer_unreference(fb); return ret; } @@ -192,8 +197,6 @@ static int intelfb_create(struct drm_fb_helper *helper, int size, ret; bool prealloc = false; - mutex_lock(&dev->struct_mutex); - if (intel_fb && (sizes->fb_width > intel_fb->base.width || sizes->fb_height > intel_fb->base.height)) { @@ -208,7 +211,7 @@ static int intelfb_create(struct drm_fb_helper *helper, DRM_DEBUG_KMS("no BIOS fb, allocating a new one\n"); ret = intelfb_alloc(helper, sizes); if (ret) - goto out_unlock; + return ret; intel_fb = ifbdev->fb; } else { DRM_DEBUG_KMS("re-using BIOS fb\n"); @@ -220,6 +223,8 @@ static int intelfb_create(struct drm_fb_helper *helper, obj = intel_fb->obj; size = obj->base.size; + mutex_lock(&dev->struct_mutex); + info = drm_fb_helper_alloc_fbi(helper); if (IS_ERR(info)) { ret = PTR_ERR(info); @@ -281,7 +286,6 @@ static int intelfb_create(struct drm_fb_helper *helper, out_unpin: i915_gem_object_ggtt_unpin(obj); drm_gem_object_unreference(&obj->base); -out_unlock: mutex_unlock(&dev->struct_mutex); return ret; }