RDMA/odp: Check for overflow when computing the umem_odp end

Since the page size can be extended in the ODP case by IB_ACCESS_HUGETLB
the existing overflow checks done by ib_umem_get() are not
sufficient. Check for overflow again.

Further, remove the unchecked math from the inlines and just use the
precomputed value stored in the interval_tree_node.

Link: https://lore.kernel.org/r/20190819111710.18440-9-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/umem_odp.c

@@ -287,19 +287,32 @@ static inline int ib_init_umem_odp(struct ib_umem_odp *umem_odp,
 
 	umem_odp->umem.is_odp = 1;
 	if (!umem_odp->is_implicit_odp) {
-		size_t pages = ib_umem_odp_num_pages(umem_odp);
+		size_t page_size = 1UL << umem_odp->page_shift;
+		size_t pages;
 
+		umem_odp->interval_tree.start =
+			ALIGN_DOWN(umem_odp->umem.address, page_size);
+		if (check_add_overflow(umem_odp->umem.address,
+				       umem_odp->umem.length,
+				       &umem_odp->interval_tree.last))
+			return -EOVERFLOW;
+		umem_odp->interval_tree.last =
+			ALIGN(umem_odp->interval_tree.last, page_size);
+		if (unlikely(umem_odp->interval_tree.last < page_size))
+			return -EOVERFLOW;
+
+		pages = (umem_odp->interval_tree.last -
+			 umem_odp->interval_tree.start) >>
+			umem_odp->page_shift;
 		if (!pages)
 			return -EINVAL;
 
 		/*
 		 * Note that the representation of the intervals in the
 		 * interval tree considers the ending point as contained in
-		 * the interval, while the function ib_umem_end returns the
-		 * first address which is not contained in the umem.
+		 * the interval.
 		 */
-		umem_odp->interval_tree.start = ib_umem_start(umem_odp);
-		umem_odp->interval_tree.last = ib_umem_end(umem_odp) - 1;
+		umem_odp->interval_tree.last--;
 
 		umem_odp->page_list = vzalloc(
 			array_size(sizeof(*umem_odp->page_list), pages));

include/rdma/ib_umem_odp.h

@@ -91,14 +91,13 @@ static inline struct ib_umem_odp *to_ib_umem_odp(struct ib_umem *umem)
 /* Returns the first page of an ODP umem. */
 static inline unsigned long ib_umem_start(struct ib_umem_odp *umem_odp)
 {
-	return ALIGN_DOWN(umem_odp->umem.address, 1UL << umem_odp->page_shift);
+	return umem_odp->interval_tree.start;
 }
 
 /* Returns the address of the page after the last one of an ODP umem. */
 static inline unsigned long ib_umem_end(struct ib_umem_odp *umem_odp)
 {
-	return ALIGN(umem_odp->umem.address + umem_odp->umem.length,
-		     1UL << umem_odp->page_shift);
+	return umem_odp->interval_tree.last + 1;
 }
 
 static inline size_t ib_umem_odp_num_pages(struct ib_umem_odp *umem_odp)