From d78d383ab354b0b9e1d23404ae0d9fbdeb9aa035 Mon Sep 17 00:00:00 2001 From: Rob Clark Date: Mon, 22 Aug 2016 15:28:38 -0400 Subject: [PATCH] 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 --- drivers/gpu/drm/msm/msm_drv.h | 6 ++++++ drivers/gpu/drm/msm/msm_gem.c | 9 +++++++++ drivers/gpu/drm/msm/msm_gem_submit.c | 3 +++ 3 files changed, 18 insertions(+) diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h index b4bc7f1ef717..d0da52f2a806 100644 --- a/drivers/gpu/drm/msm/msm_drv.h +++ b/drivers/gpu/drm/msm/msm_drv.h @@ -157,6 +157,12 @@ struct msm_drm_private { 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 6cd4af443139..85f3047e05ae 100644 --- a/drivers/gpu/drm/msm/msm_gem.c +++ b/drivers/gpu/drm/msm/msm_gem.c @@ -196,11 +196,20 @@ int msm_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf) { 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 408da409a216..880d6a9af7c8 100644 --- a/drivers/gpu/drm/msm/msm_gem_submit.c +++ b/drivers/gpu/drm/msm/msm_gem_submit.c @@ -394,6 +394,8 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data, 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 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data, if (ret) msm_gem_submit_free(submit); out_unlock: + priv->struct_mutex_task = NULL; mutex_unlock(&dev->struct_mutex); return ret; } -- GitLab