svn commit: r279599 - head/sys/dev/drm2

[Jean-Sebastien Pedron]

Author: dumbbell
Date: Wed Mar  4 20:43:46 2015
New Revision: 279599
URL: https://svnweb.freebsd.org/changeset/base/279599

Log:
  drm: Import Linux commit b7ea85a4fed37835eec78a7be3039c8dc22b8178
  
  Author: Huacai Chen <chenhc at lemote.com>
  Date:   Tue May 21 06:23:43 2013 +0000
  
      drm: fix a use-after-free when GPU acceleration disabled
  
      When GPU acceleration is disabled, drm_vblank_cleanup() will free the
      vblank-related data, such as vblank_refcount, vblank_inmodeset, etc.
      But we found that drm_vblank_post_modeset() may be called after the
      cleanup, which use vblank_refcount and vblank_inmodeset. And this will
      cause a kernel panic.
  
      Fix this by return immediately if dev->num_crtcs is zero. This is the
      same thing that drm_vblank_pre_modeset() does.
  
      Call trace of a drm_vblank_post_modeset() after drm_vblank_cleanup():
      [   62.628906] [<ffffffff804868d0>] drm_vblank_post_modeset+0x34/0xb4
      [   62.628906] [<ffffffff804c7008>] atombios_crtc_dpms+0xb4/0x174
      [   62.628906] [<ffffffff804c70e0>] atombios_crtc_commit+0x18/0x38
      [   62.628906] [<ffffffff8047f038>] drm_crtc_helper_set_mode+0x304/0x3cc
      [   62.628906] [<ffffffff8047f92c>] drm_crtc_helper_set_config+0x6d8/0x988
      [   62.628906] [<ffffffff8047dd40>] drm_fb_helper_set_par+0x94/0x104
      [   62.628906] [<ffffffff80439d14>] fbcon_init+0x424/0x57c
      [   62.628906] [<ffffffff8046a638>] visual_init+0xb8/0x118
      [   62.628906] [<ffffffff8046b9f8>] take_over_console+0x238/0x384
      [   62.628906] [<ffffffff80436df8>] fbcon_takeover+0x7c/0xdc
      [   62.628906] [<ffffffff8024fa20>] notifier_call_chain+0x44/0x94
      [   62.628906] [<ffffffff8024fcbc>] __blocking_notifier_call_chain+0x48/0x68
      [   62.628906] [<ffffffff8042d990>] register_framebuffer+0x228/0x260
      [   62.628906] [<ffffffff8047e010>] drm_fb_helper_single_fb_probe+0x260/0x314
      [   62.628906] [<ffffffff8047e2c4>] drm_fb_helper_initial_config+0x200/0x234
      [   62.628906] [<ffffffff804e5560>] radeon_fbdev_init+0xd4/0xf4
      [   62.628906] [<ffffffff804e0e08>] radeon_modeset_init+0x9bc/0xa18
      [   62.628906] [<ffffffff804bfc14>] radeon_driver_load_kms+0xdc/0x12c
      [   62.628906] [<ffffffff8048b548>] drm_get_pci_dev+0x148/0x238
      [   62.628906] [<ffffffff80423564>] local_pci_probe+0x5c/0xd0
      [   62.628906] [<ffffffff80241ac4>] work_for_cpu_fn+0x1c/0x30
      [   62.628906] [<ffffffff802427c8>] process_one_work+0x274/0x3bc
      [   62.628906] [<ffffffff80242934>] process_scheduled_works+0x24/0x44
      [   62.628906] [<ffffffff8024515c>] worker_thread+0x31c/0x3f4
      [   62.628906] [<ffffffff802497a8>] kthread+0x88/0x90
      [   62.628906] [<ffffffff80206794>] kernel_thread_helper+0x10/0x18
  
      Signed-off-by: Huacai Chen <chenhc at lemote.com>
      Signed-off-by: Binbin Zhou <zhoubb at lemote.com>
      Cc: <stable at vger.kernel.org>
      Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>
      Acked-by: Paul Menzel <paulepanter at users.sourceforge.net>
      Signed-off-by: Dave Airlie <airlied at gmail.com>
  
  Reported by:	J.R. Oldroyd <fbsd at opal.com>
  MFC after:	2 weeks

Modified:
  head/sys/dev/drm2/drm_irq.c

Modified: head/sys/dev/drm2/drm_irq.c
==============================================================================
--- head/sys/dev/drm2/drm_irq.c	Wed Mar  4 20:33:15 2015	(r279598)
+++ head/sys/dev/drm2/drm_irq.c	Wed Mar  4 20:43:46 2015	(r279599)
@@ -883,7 +883,7 @@ void drm_vblank_off(struct drm_device *d
  */
 void drm_vblank_pre_modeset(struct drm_device *dev, int crtc)
 {
-	/* vblank is not initialized (IRQ not installed ?) */
+	/* vblank is not initialized (IRQ not installed ?), or has been freed */
 	if (!dev->num_crtcs)
 		return;
 	/*
@@ -902,6 +902,9 @@ void drm_vblank_pre_modeset(struct drm_d
 
 void drm_vblank_post_modeset(struct drm_device *dev, int crtc)
 {
+	/* vblank is not initialized (IRQ not installed ?), or has been freed */
+	if (!dev->num_crtcs)
+		return;
 
 	if (dev->vblank_inmodeset[crtc]) {
 		mtx_lock(&dev->vbl_lock);