[SECURITY PATCH 16/28] relocator: Protect grub_relocator_alloc_chunk_addr() input args against integer underflow/overflow

[Daniel Kiper]

From: Alexey Makhalov <amakhalov@vmware.com>

Use arithmetic macros from safemath.h to accomplish it. In this commit,
I didn't want to be too paranoid to check every possible math equation
for overflow/underflow. Only obvious places (with non zero chance of
overflow/underflow) were refactored.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/loader/i386/linux.c    |  9 +++++++--
 grub-core/loader/i386/pc/linux.c |  9 +++++++--
 grub-core/loader/i386/xen.c      | 12 ++++++++++--
 grub-core/loader/xnu.c           | 11 +++++++----
 4 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/grub-core/loader/i386/linux.c b/grub-core/loader/i386/linux.c
index ac1fae72e..938ba536e 100644
--- a/grub-core/loader/i386/linux.c
+++ b/grub-core/loader/i386/linux.c
@@ -36,6 +36,7 @@
 #include <grub/lib/cmdline.h>
 #include <grub/linux.h>
 #include <grub/machine/kernel.h>
+#include <grub/safemath.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -547,9 +548,13 @@ grub_linux_boot (void)
 
   {
     grub_relocator_chunk_t ch;
+    grub_size_t sz;
+
+    if (grub_add (ctx.real_size, efi_mmap_size, &sz))
+      return GRUB_ERR_OUT_OF_RANGE;
+
     err = grub_relocator_alloc_chunk_addr (relocator, &ch,
-                                          ctx.real_mode_target,
-                                          (ctx.real_size + efi_mmap_size));
+                                          ctx.real_mode_target, sz);
     if (err)
      return err;
     real_mode_mem = get_virtual_current_address (ch);
diff --git a/grub-core/loader/i386/pc/linux.c b/grub-core/loader/i386/pc/linux.c
index f56af7c50..8be763d19 100644
--- a/grub-core/loader/i386/pc/linux.c
+++ b/grub-core/loader/i386/pc/linux.c
@@ -35,6 +35,7 @@
 #include <grub/i386/floppy.h>
 #include <grub/lib/cmdline.h>
 #include <grub/linux.h>
+#include <grub/safemath.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -218,8 +219,12 @@ grub_cmd_linux (grub_command_t cmd __attribute__ 
((unused)),
     setup_sects = GRUB_LINUX_DEFAULT_SETUP_SECTS;
 
   real_size = setup_sects << GRUB_DISK_SECTOR_BITS;
-  grub_linux16_prot_size = grub_file_size (file)
-    - real_size - GRUB_DISK_SECTOR_SIZE;
+  if (grub_sub (grub_file_size (file), real_size, &grub_linux16_prot_size) ||
+      grub_sub (grub_linux16_prot_size, GRUB_DISK_SECTOR_SIZE, 
&grub_linux16_prot_size))
+    {
+      grub_error (GRUB_ERR_OUT_OF_RANGE, N_("overflow is detected"));
+      goto fail;
+    }
 
   if (! grub_linux_is_bzimage
       && GRUB_LINUX_ZIMAGE_ADDR + grub_linux16_prot_size
diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
index 8f662c8ac..cd24874ca 100644
--- a/grub-core/loader/i386/xen.c
+++ b/grub-core/loader/i386/xen.c
@@ -41,6 +41,7 @@
 #include <grub/linux.h>
 #include <grub/i386/memory.h>
 #include <grub/verify.h>
+#include <grub/safemath.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -636,6 +637,7 @@ grub_cmd_xen (grub_command_t cmd __attribute__ ((unused)),
   grub_relocator_chunk_t ch;
   grub_addr_t kern_start;
   grub_addr_t kern_end;
+  grub_size_t sz;
 
   if (argc == 0)
     return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));
@@ -703,8 +705,14 @@ grub_cmd_xen (grub_command_t cmd __attribute__ ((unused)),
 
   xen_state.max_addr = ALIGN_UP (kern_end, PAGE_SIZE);
 
-  err = grub_relocator_alloc_chunk_addr (xen_state.relocator, &ch, kern_start,
-                                        kern_end - kern_start);
+
+  if (grub_sub (kern_end, kern_start, &sz))
+    {
+      err = GRUB_ERR_OUT_OF_RANGE;
+      goto fail;
+    }
+
+  err = grub_relocator_alloc_chunk_addr (xen_state.relocator, &ch, kern_start, 
sz);
   if (err)
     goto fail;
   kern_chunk_src = get_virtual_current_address (ch);
diff --git a/grub-core/loader/xnu.c b/grub-core/loader/xnu.c
index 77d7060e1..9ae4ceb35 100644
--- a/grub-core/loader/xnu.c
+++ b/grub-core/loader/xnu.c
@@ -34,6 +34,7 @@
 #include <grub/env.h>
 #include <grub/i18n.h>
 #include <grub/verify.h>
+#include <grub/safemath.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -59,15 +60,17 @@ grub_xnu_heap_malloc (int size, void **src, grub_addr_t 
*target)
 {
   grub_err_t err;
   grub_relocator_chunk_t ch;
+  grub_addr_t tgt;
+
+  if (grub_add (grub_xnu_heap_target_start, grub_xnu_heap_size, &tgt))
+    return GRUB_ERR_OUT_OF_RANGE;
   
-  err = grub_relocator_alloc_chunk_addr (grub_xnu_relocator, &ch,
-                                        grub_xnu_heap_target_start
-                                        + grub_xnu_heap_size, size);
+  err = grub_relocator_alloc_chunk_addr (grub_xnu_relocator, &ch, tgt, size);
   if (err)
     return err;
 
   *src = get_virtual_current_address (ch);
-  *target = grub_xnu_heap_target_start + grub_xnu_heap_size;
+  *target = tgt;
   grub_xnu_heap_size += size;
   grub_dprintf ("xnu", "val=%p\n", *src);
   return GRUB_ERR_NONE;
-- 
2.11.0