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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>
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3 changed files with 18 additions and 0 deletions
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@ -157,6 +157,12 @@ struct msm_drm_private {
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struct shrinker shrinker;
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struct msm_vblank_ctrl vblank_ctrl;
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/* task holding struct_mutex.. currently only used in submit path
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* to detect and reject faults from copy_from_user() for submit
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* ioctl.
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*/
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struct task_struct *struct_mutex_task;
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};
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struct msm_format {
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@ -196,11 +196,20 @@ int msm_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
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{
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struct drm_gem_object *obj = vma->vm_private_data;
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struct drm_device *dev = obj->dev;
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struct msm_drm_private *priv = dev->dev_private;
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struct page **pages;
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unsigned long pfn;
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pgoff_t pgoff;
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int ret;
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/* This should only happen if userspace tries to pass a mmap'd
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* but unfaulted gem bo vaddr into submit ioctl, triggering
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* a page fault while struct_mutex is already held. This is
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* not a valid use-case so just bail.
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*/
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if (priv->struct_mutex_task == current)
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return VM_FAULT_SIGBUS;
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/* Make sure we don't parallel update on a fault, nor move or remove
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* something from beneath our feet
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*/
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@ -394,6 +394,8 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
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if (ret)
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return ret;
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priv->struct_mutex_task = current;
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submit = submit_create(dev, gpu, args->nr_bos, args->nr_cmds);
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if (!submit) {
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ret = -ENOMEM;
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@ -485,6 +487,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
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if (ret)
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msm_gem_submit_free(submit);
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out_unlock:
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priv->struct_mutex_task = NULL;
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mutex_unlock(&dev->struct_mutex);
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return ret;
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}
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