Re: [PATCH v3 hmm 08/11] drm/radeon: use mmu_notifier_get/put for struct radeon_mn

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Am 07.08.19 um 01:15 schrieb Jason Gunthorpe:
From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>

radeon is using a device global hash table to track what mmu_notifiers
have been registered on struct mm. This is better served with the new
get/put scheme instead.

radeon has a bug where it was not blocking notifier release() until all
the BO's had been invalidated. This could result in a use after free of
pages the BOs. This is tied into a second bug where radeon left the
notifiers running endlessly even once the interval tree became
empty. This could result in a use after free with module unload.

Both are fixed by changing the lifetime model, the BOs exist in the
interval tree with their natural lifetimes independent of the mm_struct
lifetime using the get/put scheme. The release runs synchronously and just
does invalidate_start across the entire interval tree to create the
required DMA fence.

Additions to the interval tree after release are already impossible as
only current->mm is used during the add.

Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>

Acked-by: Christian König <christian.koenig@xxxxxxx>

But I'm wondering if we shouldn't completely drop radeon userptr support.

It's just to buggy,
Christian.

---
  drivers/gpu/drm/radeon/radeon.h        |   3 -
  drivers/gpu/drm/radeon/radeon_device.c |   2 -
  drivers/gpu/drm/radeon/radeon_drv.c    |   2 +
  drivers/gpu/drm/radeon/radeon_mn.c     | 157 ++++++-------------------
  4 files changed, 38 insertions(+), 126 deletions(-)

AMD team: I wonder if kfd has similar lifetime issues?

diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index 32808e50be12f8..918164f90b114a 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -2451,9 +2451,6 @@ struct radeon_device {
  	/* tracking pinned memory */
  	u64 vram_pin_size;
  	u64 gart_pin_size;
-
-	struct mutex	mn_lock;
-	DECLARE_HASHTABLE(mn_hash, 7);
  };
bool radeon_is_px(struct drm_device *dev);
diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index dceb554e567446..788b1d8a80e660 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -1325,8 +1325,6 @@ int radeon_device_init(struct radeon_device *rdev,
  	init_rwsem(&rdev->pm.mclk_lock);
  	init_rwsem(&rdev->exclusive_lock);
  	init_waitqueue_head(&rdev->irq.vblank_queue);
-	mutex_init(&rdev->mn_lock);
-	hash_init(rdev->mn_hash);
  	r = radeon_gem_init(rdev);
  	if (r)
  		return r;
diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
index a6cbe11f79c611..b6535ac91fdb74 100644
--- a/drivers/gpu/drm/radeon/radeon_drv.c
+++ b/drivers/gpu/drm/radeon/radeon_drv.c
@@ -35,6 +35,7 @@
  #include <linux/module.h>
  #include <linux/pm_runtime.h>
  #include <linux/vga_switcheroo.h>
+#include <linux/mmu_notifier.h>
#include <drm/drm_crtc_helper.h>
  #include <drm/drm_drv.h>
@@ -624,6 +625,7 @@ static void __exit radeon_exit(void)
  {
  	pci_unregister_driver(pdriver);
  	radeon_unregister_atpx_handler();
+	mmu_notifier_synchronize();
  }
module_init(radeon_init);
diff --git a/drivers/gpu/drm/radeon/radeon_mn.c b/drivers/gpu/drm/radeon/radeon_mn.c
index 8c3871ed23a9f0..fc8254273a800b 100644
--- a/drivers/gpu/drm/radeon/radeon_mn.c
+++ b/drivers/gpu/drm/radeon/radeon_mn.c
@@ -37,17 +37,8 @@
  #include "radeon.h"
struct radeon_mn {
-	/* constant after initialisation */
-	struct radeon_device	*rdev;
-	struct mm_struct	*mm;
  	struct mmu_notifier	mn;
- /* only used on destruction */
-	struct work_struct	work;
-
-	/* protected by rdev->mn_lock */
-	struct hlist_node	node;
-
  	/* objects protected by lock */
  	struct mutex		lock;
  	struct rb_root_cached	objects;
@@ -58,55 +49,6 @@ struct radeon_mn_node {
  	struct list_head		bos;
  };
-/**
- * radeon_mn_destroy - destroy the rmn
- *
- * @work: previously sheduled work item
- *
- * Lazy destroys the notifier from a work item
- */
-static void radeon_mn_destroy(struct work_struct *work)
-{
-	struct radeon_mn *rmn = container_of(work, struct radeon_mn, work);
-	struct radeon_device *rdev = rmn->rdev;
-	struct radeon_mn_node *node, *next_node;
-	struct radeon_bo *bo, *next_bo;
-
-	mutex_lock(&rdev->mn_lock);
-	mutex_lock(&rmn->lock);
-	hash_del(&rmn->node);
-	rbtree_postorder_for_each_entry_safe(node, next_node,
-					     &rmn->objects.rb_root, it.rb) {
-
-		interval_tree_remove(&node->it, &rmn->objects);
-		list_for_each_entry_safe(bo, next_bo, &node->bos, mn_list) {
-			bo->mn = NULL;
-			list_del_init(&bo->mn_list);
-		}
-		kfree(node);
-	}
-	mutex_unlock(&rmn->lock);
-	mutex_unlock(&rdev->mn_lock);
-	mmu_notifier_unregister(&rmn->mn, rmn->mm);
-	kfree(rmn);
-}
-
-/**
- * radeon_mn_release - callback to notify about mm destruction
- *
- * @mn: our notifier
- * @mn: the mm this callback is about
- *
- * Shedule a work item to lazy destroy our notifier.
- */
-static void radeon_mn_release(struct mmu_notifier *mn,
-			      struct mm_struct *mm)
-{
-	struct radeon_mn *rmn = container_of(mn, struct radeon_mn, mn);
-	INIT_WORK(&rmn->work, radeon_mn_destroy);
-	schedule_work(&rmn->work);
-}
-
  /**
   * radeon_mn_invalidate_range_start - callback to notify about mm change
   *
@@ -183,65 +125,44 @@ static int radeon_mn_invalidate_range_start(struct mmu_notifier *mn,
  	return ret;
  }
-static const struct mmu_notifier_ops radeon_mn_ops = {
-	.release = radeon_mn_release,
-	.invalidate_range_start = radeon_mn_invalidate_range_start,
-};
+static void radeon_mn_release(struct mmu_notifier *mn, struct mm_struct *mm)
+{
+	struct mmu_notifier_range range = {
+		.mm = mm,
+		.start = 0,
+		.end = ULONG_MAX,
+		.flags = 0,
+		.event = MMU_NOTIFY_UNMAP,
+	};
+
+	radeon_mn_invalidate_range_start(mn, &range);
+}
-/**
- * radeon_mn_get - create notifier context
- *
- * @rdev: radeon device pointer
- *
- * Creates a notifier context for current->mm.
- */
-static struct radeon_mn *radeon_mn_get(struct radeon_device *rdev)
+static struct mmu_notifier *radeon_mn_alloc_notifier(struct mm_struct *mm)
  {
-	struct mm_struct *mm = current->mm;
  	struct radeon_mn *rmn;
-	int r;
-
-	if (down_write_killable(&mm->mmap_sem))
-		return ERR_PTR(-EINTR);
-
-	mutex_lock(&rdev->mn_lock);
-
-	hash_for_each_possible(rdev->mn_hash, rmn, node, (unsigned long)mm)
-		if (rmn->mm == mm)
-			goto release_locks;
rmn = kzalloc(sizeof(*rmn), GFP_KERNEL);
-	if (!rmn) {
-		rmn = ERR_PTR(-ENOMEM);
-		goto release_locks;
-	}
+	if (!rmn)
+		return ERR_PTR(-ENOMEM);
- rmn->rdev = rdev;
-	rmn->mm = mm;
-	rmn->mn.ops = &radeon_mn_ops;
  	mutex_init(&rmn->lock);
  	rmn->objects = RB_ROOT_CACHED;
-	
-	r = __mmu_notifier_register(&rmn->mn, mm);
-	if (r)
-		goto free_rmn;
-
-	hash_add(rdev->mn_hash, &rmn->node, (unsigned long)mm);
-
-release_locks:
-	mutex_unlock(&rdev->mn_lock);
-	up_write(&mm->mmap_sem);
-
-	return rmn;
-
-free_rmn:
-	mutex_unlock(&rdev->mn_lock);
-	up_write(&mm->mmap_sem);
-	kfree(rmn);
+	return &rmn->mn;
+}
- return ERR_PTR(r);
+static void radeon_mn_free_notifier(struct mmu_notifier *mn)
+{
+	kfree(container_of(mn, struct radeon_mn, mn));
  }
+static const struct mmu_notifier_ops radeon_mn_ops = {
+	.release = radeon_mn_release,
+	.invalidate_range_start = radeon_mn_invalidate_range_start,
+	.alloc_notifier = radeon_mn_alloc_notifier,
+	.free_notifier = radeon_mn_free_notifier,
+};
+
  /**
   * radeon_mn_register - register a BO for notifier updates
   *
@@ -254,15 +175,16 @@ static struct radeon_mn *radeon_mn_get(struct radeon_device *rdev)
  int radeon_mn_register(struct radeon_bo *bo, unsigned long addr)
  {
  	unsigned long end = addr + radeon_bo_size(bo) - 1;
-	struct radeon_device *rdev = bo->rdev;
+	struct mmu_notifier *mn;
  	struct radeon_mn *rmn;
  	struct radeon_mn_node *node = NULL;
  	struct list_head bos;
  	struct interval_tree_node *it;
- rmn = radeon_mn_get(rdev);
-	if (IS_ERR(rmn))
-		return PTR_ERR(rmn);
+	mn = mmu_notifier_get(&radeon_mn_ops, current->mm);
+	if (IS_ERR(mn))
+		return PTR_ERR(mn);
+	rmn = container_of(mn, struct radeon_mn, mn);
INIT_LIST_HEAD(&bos); @@ -309,22 +231,13 @@ int radeon_mn_register(struct radeon_bo *bo, unsigned long addr)
   */
  void radeon_mn_unregister(struct radeon_bo *bo)
  {
-	struct radeon_device *rdev = bo->rdev;
-	struct radeon_mn *rmn;
+	struct radeon_mn *rmn = bo->mn;
  	struct list_head *head;
- mutex_lock(&rdev->mn_lock);
-	rmn = bo->mn;
-	if (rmn == NULL) {
-		mutex_unlock(&rdev->mn_lock);
-		return;
-	}
-
  	mutex_lock(&rmn->lock);
  	/* save the next list entry for later */
  	head = bo->mn_list.next;
- bo->mn = NULL;
  	list_del(&bo->mn_list);
if (list_empty(head)) {
@@ -335,5 +248,7 @@ void radeon_mn_unregister(struct radeon_bo *bo)
  	}
mutex_unlock(&rmn->lock);
-	mutex_unlock(&rdev->mn_lock);
+
+	mmu_notifier_put(&rmn->mn);
+	bo->mn = NULL;
  }

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