drm/msm: protect against faults from copy_from_user() in submit ioctl
An evil userspace could try to cause deadlock by passing an unfaulted-in
GEM bo as submit->bos (or submit->cmds) table. Which will trigger
msm_gem_fault() while we already hold struct_mutex. See:
https://github.com/freedreno/msmtest/blob/master/evilsubmittest.c
Cc: stable@vger.kernel.org
Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index b4bc7f1..d0da52f 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -157,6 +157,12 @@
struct shrinker shrinker;
struct msm_vblank_ctrl vblank_ctrl;
+
+ /* task holding struct_mutex.. currently only used in submit path
+ * to detect and reject faults from copy_from_user() for submit
+ * ioctl.
+ */
+ struct task_struct *struct_mutex_task;
};
struct msm_format {
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 6cd4af4..85f3047 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -196,11 +196,20 @@
{
struct drm_gem_object *obj = vma->vm_private_data;
struct drm_device *dev = obj->dev;
+ struct msm_drm_private *priv = dev->dev_private;
struct page **pages;
unsigned long pfn;
pgoff_t pgoff;
int ret;
+ /* This should only happen if userspace tries to pass a mmap'd
+ * but unfaulted gem bo vaddr into submit ioctl, triggering
+ * a page fault while struct_mutex is already held. This is
+ * not a valid use-case so just bail.
+ */
+ if (priv->struct_mutex_task == current)
+ return VM_FAULT_SIGBUS;
+
/* Make sure we don't parallel update on a fault, nor move or remove
* something from beneath our feet
*/
diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
index 408da40..880d6a9 100644
--- a/drivers/gpu/drm/msm/msm_gem_submit.c
+++ b/drivers/gpu/drm/msm/msm_gem_submit.c
@@ -394,6 +394,8 @@
if (ret)
return ret;
+ priv->struct_mutex_task = current;
+
submit = submit_create(dev, gpu, args->nr_bos, args->nr_cmds);
if (!submit) {
ret = -ENOMEM;
@@ -485,6 +487,7 @@
if (ret)
msm_gem_submit_free(submit);
out_unlock:
+ priv->struct_mutex_task = NULL;
mutex_unlock(&dev->struct_mutex);
return ret;
}