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drm/panfrost: Prevent race when handling page fault

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When handling a GPU page fault addr_to_drm_mm_node() is used to
translate the GPU address to a buffer object. However it is possible for
the buffer object to be freed after the function has returned resulting
in a use-after-free of the BO.

Change addr_to_drm_mm_node to return the panfrost_gem_object with an
extra reference on it, preventing the BO from being freed until after
the page fault has been handled.

Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190913160310.50444-1-steven.price@arm.com
This commit is contained in:
Steven Price 2019-09-13 17:03:10 +01:00 committed by Rob Herring
parent d18a966204
commit 65e51e30d8
1 changed files with 36 additions and 19 deletions
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55
drivers/gpu/drm/panfrost/panfrost_mmu.c
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@ -386,28 +386,40 @@ void panfrost_mmu_pgtable_free(struct panfrost_file_priv *priv)
free_io_pgtable_ops(mmu->pgtbl_ops);
}
static struct drm_mm_node *addr_to_drm_mm_node(struct panfrost_device *pfdev, int as, u64 addr)
static struct panfrost_gem_object *
addr_to_drm_mm_node(struct panfrost_device *pfdev, int as, u64 addr)
{
struct drm_mm_node *node = NULL;
struct panfrost_gem_object *bo = NULL;
struct panfrost_file_priv *priv;
struct drm_mm_node *node;
u64 offset = addr >> PAGE_SHIFT;
struct panfrost_mmu *mmu;
spin_lock(&pfdev->as_lock);
list_for_each_entry(mmu, &pfdev->as_lru_list, list) {
struct panfrost_file_priv *priv;
if (as != mmu->as)
continue;
if (as == mmu->as)
break;
}
if (as != mmu->as)
goto out;
priv = container_of(mmu, struct panfrost_file_priv, mmu);
drm_mm_for_each_node(node, &priv->mm) {
if (offset >= node->start && offset < (node->start + node->size))
goto out;
priv = container_of(mmu, struct panfrost_file_priv, mmu);
spin_lock(&priv->mm_lock);
drm_mm_for_each_node(node, &priv->mm) {
if (offset >= node->start &&
offset < (node->start + node->size)) {
bo = drm_mm_node_to_panfrost_bo(node);
drm_gem_object_get(&bo->base.base);
break;
}
}
spin_unlock(&priv->mm_lock);
out:
spin_unlock(&pfdev->as_lock);
return node;
return bo;
}
#define NUM_FAULT_PAGES (SZ_2M / PAGE_SIZE)
@ -415,29 +427,28 @@ static struct drm_mm_node *addr_to_drm_mm_node(struct panfrost_device *pfdev, in
int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as, u64 addr)
{
int ret, i;
struct drm_mm_node *node;
struct panfrost_gem_object *bo;
struct address_space *mapping;
pgoff_t page_offset;
struct sg_table *sgt;
struct page **pages;
node = addr_to_drm_mm_node(pfdev, as, addr);
if (!node)
bo = addr_to_drm_mm_node(pfdev, as, addr);
if (!bo)
return -ENOENT;
bo = drm_mm_node_to_panfrost_bo(node);
if (!bo->is_heap) {
dev_WARN(pfdev->dev, "matching BO is not heap type (GPU VA = %llx)",
node->start << PAGE_SHIFT);
return -EINVAL;
bo->node.start << PAGE_SHIFT);
ret = -EINVAL;
goto err_bo;
}
WARN_ON(bo->mmu->as != as);
/* Assume 2MB alignment and size multiple */
addr &= ~((u64)SZ_2M - 1);
page_offset = addr >> PAGE_SHIFT;
page_offset -= node->start;
page_offset -= bo->node.start;
mutex_lock(&bo->base.pages_lock);
@ -446,7 +457,8 @@ int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as, u64 addr)
sizeof(struct sg_table), GFP_KERNEL | __GFP_ZERO);
if (!bo->sgts) {
mutex_unlock(&bo->base.pages_lock);
return -ENOMEM;
ret = -ENOMEM;
goto err_bo;
}
pages = kvmalloc_array(bo->base.base.size >> PAGE_SHIFT,
@ -455,7 +467,8 @@ int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as, u64 addr)
kfree(bo->sgts);
bo->sgts = NULL;
mutex_unlock(&bo->base.pages_lock);
return -ENOMEM;
ret = -ENOMEM;
goto err_bo;
}
bo->base.pages = pages;
bo->base.pages_use_count = 1;
@ -493,12 +506,16 @@ int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as, u64 addr)
dev_dbg(pfdev->dev, "mapped page fault @ AS%d %llx", as, addr);
drm_gem_object_put_unlocked(&bo->base.base);
return 0;
err_map:
sg_free_table(sgt);
err_pages:
drm_gem_shmem_put_pages(&bo->base);
err_bo:
drm_gem_object_put_unlocked(&bo->base.base);
return ret;
}