[098/141] drm: fix a use-after-free when GPU acceleration disabled

Steven Rostedt
2013-07-03T19:08:46Z

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: 0098-drm-fix-a-use-after-free-when-GPU-acceleration-disab.patch --]
[-- Type: text/plain, Size: 3676 bytes --]

3.6.11.6 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Huacai Chen <chenhc@lemote.com>

[ Upstream commit b7ea85a4fed37835eec78a7be3039c8dc22b8178 ]

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@lemote.com>
Signed-off-by: Binbin Zhou <zhoubb@lemote.com>
Cc: <stable@vger.kernel.org>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Acked-by: Paul Menzel <paulepanter@users.sourceforge.net>
Signed-off-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
drivers/gpu/drm/drm_irq.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 03f16f3..275bc82 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -980,7 +980,7 @@ EXPORT_SYMBOL(drm_vblank_off);
*/
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;
/*
@@ -1002,6 +1002,10 @@ void drm_vblank_post_modeset(struct drm_device *dev, int crtc)
{
unsigned long irqflags;

+ /* vblank is not initialized (IRQ not installed ?), or has been freed */
+ if (!dev->num_crtcs)
+ return;
+
if (dev->vblank_inmodeset[crtc]) {
spin_lock_irqsave(&dev->vbl_lock, irqflags);
dev->vblank_disable_allowed = 1;
--
1.7.10.4