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Subject[PATCH v3 hmm 08/11] drm/radeon: use mmu_notifier_get/put for struct radeon_mn
Date
From: Jason Gunthorpe <jgg@mellanox.com>

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@mellanox.com>
---
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;
}
--
2.22.0
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