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 --- Changes since v1: * Hold the mm_lock around drm_mm_for_each_node()

I've also posted a new IGT test for this: https://patchwork.freedesktop.org/patch/330513/

drivers/gpu/drm/panfrost/panfrost_mmu.c | 55 ++++++++++++++++--------- 1 file changed, 36 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c index 842bdd7cf6be..b6b281896ed6 100644 --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c @@ -392,28 +392,40 @@ 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);

- 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; + 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) @@ -421,29 +433,28 @@ 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);

@@ -452,7 +463,8 @@ 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, @@ -461,7 +473,8 @@ 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; @@ -499,12 +512,16 @@ 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; }