IB/uverbs: Prevent integer overflow in ib_umem_get address arithmetic

Properly verify that the resulting page aligned end address is larger
than both the start address and the length of the memory area requested.

Both the start and length arguments for ib_umem_get are controlled by
the user. A misbehaving user can provide values which will cause an
integer overflow when calculating the page aligned end address.

This overflow can cause also miscalculation of the number of pages
mapped, and additional logic issues.

Addresses: CVE-2014-8159
Cc: <stable@vger.kernel.org>
Signed-off-by: NShachar Raindel <raindel@mellanox.com>
Signed-off-by: NJack Morgenstein <jackm@mellanox.com>
Signed-off-by: NOr Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>

drivers/infiniband/core/umem.c

@@ -99,6 +99,14 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
 	if (dmasync)
 		dma_set_attr(DMA_ATTR_WRITE_BARRIER, &attrs);
 
+	/*
+	 * If the combination of the addr and size requested for this memory
+	 * region causes an integer overflow, return error.
+	 */
+	if ((PAGE_ALIGN(addr + size) <= size) ||
+	    (PAGE_ALIGN(addr + size) <= addr))
+		return ERR_PTR(-EINVAL);
+
 	if (!can_do_mlock())
 		return ERR_PTR(-EPERM);