Improve overflow checks in bytevector, string, and I/O operations.

* libguile/bytevectors.c (INTEGER_ACCESSOR_PROLOGUE)
(scm_bytevector_copy_x, bytevector_large_set): Rewrite checks to reliably
detect overflows.
(make_bytevector): Constrain the bytevector length to avoid later
overflows during allocation.
(make_bytevector_from_buffer): Fix indentation.
(scm_bytevector_length): Use 'scm_from_size_t' to convert a 'size_t',
not 'scm_from_uint'.
* libguile/fports.c (fport_seek): Check for overflow before the implicit
conversion of the return value.
* libguile/guardians.c (guardian_print): Use 'scm_from_ulong' to convert
an 'unsigned long', not 'scm_from_uint'.
* libguile/ports.c (scm_unread_string): Change a variable to type 'size_t'.
(scm_seek, scm_truncate_file): Use 'scm_t_off' instead of
'off_t_or_off64_t' to avoid implicit type conversions that could
overflow, because 'ptob->seek' and 'ptob->truncate' use 'scm_t_off'.
* libguile/r6rs-ports.c (bytevector_input_port_seek)
(custom_binary_port_seek, bytevector_output_port_seek): Rewrite offset
calculations to reliably detect overflows.  Use 'scm_from_off_t' to
convert a 'scm_t_off', not 'scm_from_long' nor 'scm_from_int'.
(scm_get_bytevector_n_x, scm_get_bytevector_all, scm_unget_bytevector)
(bytevector_output_port_write): Rewrite checks to reliably detect
overflows.  Use 'size_t' where appropriate.
(bytevector_output_port_buffer_grow): Rewrite size calculations to
reliably detect overflows.  Minor change in the calculation of the new
size: now it is max(min_size, 2*current_size), whereas previously it
would multiply current_size by the smallest power of 2 needed to surpass
min_size.
* libguile/strings.c (make_stringbuf): Constrain the stringbuf length to
avoid later overflows during allocation.
(scm_string_append): Change overflow check to use INT_ADD_OVERFLOW.
* libguile/strports.c (string_port_write): Rewrite size calculations to
reliably detect overflows.
(string_port_seek): Rewrite offset calculations to reliably detect
overflows.  Use 'scm_from_off_t' to convert a 'scm_t_off', not
'scm_from_long'.
(string_port_truncate): Use 'scm_from_off_t' to convert a 'scm_t_off',
not 'scm_from_off_t_or_off64_t'.
* libguile/vectors.c (scm_c_make_vector): Change a variable to type
'size_t'.

1 files changed, 22 insertions, 9 deletions

diff --git a/libguile/strports.c b/libguile/strports.c
index b01282ee1..876a62a86 100644
--- a/libguile/strports.c
+++ b/libguile/strports.c
@@ -1,5 +1,5 @@
 /* Copyright (C) 1995, 1996, 1998-2003, 2005, 2006, 2009-2014,
- *   2016-2018 Free Software Foundation, Inc.
+ *   2016-2019 Free Software Foundation, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -28,6 +28,7 @@
 
 #include <stdio.h>
 #include <unistd.h>
+#include <intprops.h>
 
 #include "libguile/bytevectors.h"
 #include "libguile/eval.h"
@@ -82,16 +83,21 @@ string_port_read (SCM port, SCM dst, size_t start, size_t count)
 
 static size_t
 string_port_write (SCM port, SCM src, size_t start, size_t count)
+#define FUNC_NAME "string_port_write"
 {
   struct string_port *stream = (void *) SCM_STREAM (port);
+  size_t old_size = SCM_BYTEVECTOR_LENGTH (stream->bytevector);
 
-  if (SCM_BYTEVECTOR_LENGTH (stream->bytevector) < stream->pos + count)
+  if (count > old_size - stream->pos)
     {
       SCM new_bv;
       size_t new_size;
 
-      new_size = max (SCM_BYTEVECTOR_LENGTH (stream->bytevector) * 2,
-                      stream->pos + count);
+      if (INT_ADD_OVERFLOW (stream->pos, count))
+        scm_num_overflow (FUNC_NAME);
+
+      /* If (old_size * 2) overflows, it's harmless.  */
+      new_size = max (old_size * 2, stream->pos + count);
       new_bv = scm_c_make_bytevector (new_size);
       memcpy (SCM_BYTEVECTOR_CONTENTS (new_bv),
               SCM_BYTEVECTOR_CONTENTS (stream->bytevector),
@@ -108,27 +114,34 @@ string_port_write (SCM port, SCM src, size_t start, size_t count)
 
   return count;
 }
+#undef FUNC_NAME
 
 static scm_t_off
 string_port_seek (SCM port, scm_t_off offset, int whence)
 #define FUNC_NAME "string_port_seek"
 {
   struct string_port *stream = (void *) SCM_STREAM (port);
+  size_t base;
   scm_t_off target;
 
   if (whence == SEEK_CUR)
-    target = offset + stream->pos;
+    base = stream->pos;
   else if (whence == SEEK_SET)
-    target = offset;
+    base = 0;
   else if (whence == SEEK_END)
-    target = offset + stream->len;
+    base = stream->len;
   else
     scm_wrong_type_arg_msg (FUNC_NAME, 0, port, "invalid `seek' parameter");
 
+  if (base > SCM_T_OFF_MAX
+      || INT_ADD_OVERFLOW ((scm_t_off) base, offset))
+    scm_num_overflow (FUNC_NAME);
+  target = (scm_t_off) base + offset;
+
   if (target >= 0 && target <= stream->len)
     stream->pos = target;
   else
-    scm_out_of_range (FUNC_NAME, scm_from_long (offset));
+    scm_out_of_range (FUNC_NAME, scm_from_off_t (offset));
 
   return target;
 }
@@ -143,7 +156,7 @@ string_port_truncate (SCM port, scm_t_off length)
   if (0 <= length && stream->pos <= length && length <= stream->len)
     stream->len = length;
   else
-    scm_out_of_range (FUNC_NAME, scm_from_off_t_or_off64_t (length));
+    scm_out_of_range (FUNC_NAME, scm_from_off_t (length));
 }
 #undef FUNC_NAME