vfio/type1: sanitize for overflow using check_*_overflow()

Adopt check_*_overflow() functions to clearly express overflow check
intent.

Tested-by: Alejandro Jimenez <[e-mail]>
Fixes: 73fa0d10d077 ("vfio: Type1 IOMMU implementation")
Reviewed-by: Jason Gunthorpe <[e-mail]>
Reviewed-by: Alejandro Jimenez <[e-mail]>
Signed-off-by: Alex Mastro <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alex Williamson <[e-mail]>

drivers/vfio/vfio_iommu_type1.c

···
 #include <linux/workqueue.h>
 #include <linux/notifier.h>
 #include <linux/mm_inline.h>
+#include <linux/overflow.h>
 #include "vfio.h"
 
 #define DRIVER_VERSION  "0.2"
···
 }
 
 static struct rb_node *vfio_find_dma_first_node(struct vfio_iommu *iommu,
-						dma_addr_t start, u64 size)
+						dma_addr_t start, size_t size)
 {
 	struct rb_node *res = NULL;
 	struct rb_node *node = iommu->dma_list.rb_node;
···
 	unsigned long remote_vaddr;
 	struct vfio_dma *dma;
 	bool do_accounting;
+	dma_addr_t iova_end;
+	size_t iova_size;
 
-	if (!iommu || !pages)
+	if (!iommu || !pages || npage <= 0)
 		return -EINVAL;
 
 	/* Supported for v2 version only */
 	if (!iommu->v2)
 		return -EACCES;
+
+	if (check_mul_overflow(npage, PAGE_SIZE, &iova_size) ||
+	    check_add_overflow(user_iova, iova_size - 1, &iova_end))
+		return -EOVERFLOW;
 
 	mutex_lock(&iommu->lock);
 
···
 {
 	struct vfio_iommu *iommu = iommu_data;
 	bool do_accounting;
+	dma_addr_t iova_end;
+	size_t iova_size;
 	int i;
 
 	/* Supported for v2 version only */
 	if (WARN_ON(!iommu->v2))
+		return;
+
+	if (WARN_ON(npage <= 0))
+		return;
+
+	if (WARN_ON(check_mul_overflow(npage, PAGE_SIZE, &iova_size) ||
+		    check_add_overflow(user_iova, iova_size - 1, &iova_end)))
 		return;
 
 	mutex_lock(&iommu->lock);
···
 	int ret = -EINVAL, retries = 0;
 	unsigned long pgshift;
 	dma_addr_t iova = unmap->iova;
-	u64 size = unmap->size;
+	dma_addr_t iova_end;
+	size_t size = unmap->size;
 	bool unmap_all = unmap->flags & VFIO_DMA_UNMAP_FLAG_ALL;
 	bool invalidate_vaddr = unmap->flags & VFIO_DMA_UNMAP_FLAG_VADDR;
 	struct rb_node *n, *first_n;
···
 		goto unlock;
 	}
 
+	if (iova != unmap->iova || size != unmap->size) {
+		ret = -EOVERFLOW;
+		goto unlock;
+	}
+
 	pgshift = __ffs(iommu->pgsize_bitmap);
 	pgsize = (size_t)1 << pgshift;
 
···
 	if (unmap_all) {
 		if (iova || size)
 			goto unlock;
-		size = U64_MAX;
-	} else if (!size || size & (pgsize - 1) ||
-		   iova + size - 1 < iova || size > SIZE_MAX) {
-		goto unlock;
+		size = SIZE_MAX;
+	} else {
+		if (!size || size & (pgsize - 1))
+			goto unlock;
+
+		if (check_add_overflow(iova, size - 1, &iova_end)) {
+			ret = -EOVERFLOW;
+			goto unlock;
+		}
 	}
 
 	/* When dirty tracking is enabled, allow only min supported pgsize */
···
 		if (dma && dma->iova != iova)
 			goto unlock;
 
-		dma = vfio_find_dma(iommu, iova + size - 1, 0);
+		dma = vfio_find_dma(iommu, iova_end, 0);
 		if (dma && dma->iova + dma->size != iova + size)
 			goto unlock;
 	}
···
 {
 	bool set_vaddr = map->flags & VFIO_DMA_MAP_FLAG_VADDR;
 	dma_addr_t iova = map->iova;
+	dma_addr_t iova_end;
 	unsigned long vaddr = map->vaddr;
+	unsigned long vaddr_end;
 	size_t size = map->size;
 	int ret = 0, prot = 0;
 	size_t pgsize;
···
 
 	/* Verify that none of our __u64 fields overflow */
 	if (map->size != size || map->vaddr != vaddr || map->iova != iova)
+		return -EOVERFLOW;
+
+	if (!size)
 		return -EINVAL;
+
+	if (check_add_overflow(iova, size - 1, &iova_end) ||
+	    check_add_overflow(vaddr, size - 1, &vaddr_end))
+		return -EOVERFLOW;
 
 	/* READ/WRITE from device perspective */
 	if (map->flags & VFIO_DMA_MAP_FLAG_WRITE)
···
 
 	WARN_ON((pgsize - 1) & PAGE_MASK);
 
-	if (!size || (size | iova | vaddr) & (pgsize - 1)) {
-		ret = -EINVAL;
-		goto out_unlock;
-	}
-
-	/* Don't allow IOVA or virtual address wrap */
-	if (iova + size - 1 < iova || vaddr + size - 1 < vaddr) {
+	if ((size | iova | vaddr) & (pgsize - 1)) {
 		ret = -EINVAL;
 		goto out_unlock;
 	}
···
 		goto out_unlock;
 	}
 
-	if (!vfio_iommu_iova_dma_valid(iommu, iova, iova + size - 1)) {
+	if (!vfio_iommu_iova_dma_valid(iommu, iova, iova_end)) {
 		ret = -EINVAL;
 		goto out_unlock;
 	}
···
 		struct vfio_iommu_type1_dirty_bitmap_get range;
 		unsigned long pgshift;
 		size_t data_size = dirty.argsz - minsz;
-		size_t iommu_pgsize;
+		size_t size, iommu_pgsize;
+		dma_addr_t iova, iova_end;
 
 		if (!data_size || data_size < sizeof(range))
 			return -EINVAL;
···
 				   sizeof(range)))
 			return -EFAULT;
 
-		if (range.iova + range.size < range.iova)
+		iova = range.iova;
+		size = range.size;
+
+		if (iova != range.iova || size != range.size)
+			return -EOVERFLOW;
+
+		if (!size)
 			return -EINVAL;
+
+		if (check_add_overflow(iova, size - 1, &iova_end))
+			return -EOVERFLOW;
+
 		if (!access_ok((void __user *)range.bitmap.data,
 			       range.bitmap.size))
 			return -EINVAL;
 
 		pgshift = __ffs(range.bitmap.pgsize);
-		ret = verify_bitmap_size(range.size >> pgshift,
+		ret = verify_bitmap_size(size >> pgshift,
 					 range.bitmap.size);
 		if (ret)
 			return ret;
···
 			ret = -EINVAL;
 			goto out_unlock;
 		}
-		if (range.iova & (iommu_pgsize - 1)) {
+		if (iova & (iommu_pgsize - 1)) {
 			ret = -EINVAL;
 			goto out_unlock;
 		}
-		if (!range.size || range.size & (iommu_pgsize - 1)) {
+		if (size & (iommu_pgsize - 1)) {
 			ret = -EINVAL;
 			goto out_unlock;
 		}
 
 		if (iommu->dirty_page_tracking)
 			ret = vfio_iova_dirty_bitmap(range.bitmap.data,
-						     iommu, range.iova,
-						     range.size,
+						     iommu, iova, size,
 						     range.bitmap.pgsize);
 		else
 			ret = -EINVAL;