elf-ops.h: fix int overflow in load_elf()

This patch fixes a possible integer overflow when we calculate
the total size of ELF segments loaded.

Reported-by: Coverity (CID 1405299)
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: NStefano Garzarella <sgarzare@redhat.com>
Message-Id: <20190910124828.39794-1-sgarzare@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/core/loader.c

@@ -338,6 +338,8 @@ const char *load_elf_strerror(int error)
         return "The image is from incompatible architecture";
     case ELF_LOAD_WRONG_ENDIAN:
         return "The image has incorrect endianness";
+    case ELF_LOAD_TOO_BIG:
+        return "The image segments are too big to load";
     default:
         return "Unknown error";
     }

include/hw/elf_ops.h

@@ -485,6 +485,11 @@ static int glue(load_elf, SZ)(const char *name, int fd,
                 }
             }
 
+            if (mem_size > INT_MAX - total_size) {
+                ret = ELF_LOAD_TOO_BIG;
+                goto fail;
+            }
+
             /* address_offset is hack for kernel images that are
                linked at the wrong physical address.  */
             if (translate_fn) {

include/hw/loader.h

@@ -89,6 +89,7 @@ int load_image_gzipped(const char *filename, hwaddr addr, uint64_t max_sz);
 #define ELF_LOAD_NOT_ELF      -2
 #define ELF_LOAD_WRONG_ARCH   -3
 #define ELF_LOAD_WRONG_ENDIAN -4
+#define ELF_LOAD_TOO_BIG      -5
 const char *load_elf_strerror(int error);
 
 /** load_elf_ram_sym: