[Emacs-diffs] /srv/bzr/emacs/trunk r103894: * sysdep.c (emacs_read, emacs_write): Check for negative sizes

[Paul Eggert]

------------------------------------------------------------
revno: 103894
committer: Paul Eggert <address@hidden>
branch nick: trunk
timestamp: Tue 2011-04-12 01:12:01 -0700
message:
  * sysdep.c (emacs_read, emacs_write): Check for negative sizes
  
  since callers should never pass a negative size.
  Change the signature to match that of plain 'read' and 'write'; see
  <http://lists.gnu.org/archive/html/emacs-devel/2011-04/msg00397.html>.
  * lisp.h: Update prototypes of emacs_write and emacs_read.
modified:
  src/ChangeLog
  src/lisp.h
  src/sysdep.c

=== modified file 'src/ChangeLog'
--- a/src/ChangeLog     2011-04-11 16:39:09 +0000
+++ b/src/ChangeLog     2011-04-12 08:12:01 +0000
@@ -1,3 +1,11 @@
+2011-04-12  Paul Eggert  <address@hidden>
+
+       * sysdep.c (emacs_read, emacs_write): Check for negative sizes
+       since callers should never pass a negative size.
+       Change the signature to match that of plain 'read' and 'write'; see
+       <http://lists.gnu.org/archive/html/emacs-devel/2011-04/msg00397.html>.
+       * lisp.h: Update prototypes of emacs_write and emacs_read.
+
 2011-04-11  Eli Zaretskii  <address@hidden>
 
        * xdisp.c (redisplay_window): Don't try to determine the character

=== modified file 'src/lisp.h'
--- a/src/lisp.h        2011-04-10 20:43:08 +0000
+++ b/src/lisp.h        2011-04-12 08:12:01 +0000
@@ -3346,8 +3346,8 @@
 extern void seed_random (long);
 extern int emacs_open (const char *, int, int);
 extern int emacs_close (int);
-extern ssize_t emacs_read (int, char *, ssize_t);
-extern ssize_t emacs_write (int, const char *, ssize_t);
+extern ssize_t emacs_read (int, char *, size_t);
+extern ssize_t emacs_write (int, const char *, size_t);
 enum { READLINK_BUFSIZE = 1024 };
 extern char *emacs_readlink (const char *, char [READLINK_BUFSIZE]);
 #ifndef HAVE_MEMSET

=== modified file 'src/sysdep.c'
--- a/src/sysdep.c      2011-04-10 20:43:08 +0000
+++ b/src/sysdep.c      2011-04-12 08:12:01 +0000
@@ -1826,10 +1826,18 @@
 }
 
 ssize_t
-emacs_read (int fildes, char *buf, ssize_t nbyte)
+emacs_read (int fildes, char *buf, size_t nbyte)
 {
   register ssize_t rtnval;
 
+  /* Defend against the possibility that a buggy caller passes a negative NBYTE
+     argument, which would be converted to a large unsigned size_t NBYTE.  This
+     defense prevents callers from doing large writes, unfortunately.  This
+     size restriction can be removed once we have carefully checked that there
+     are no such callers.  */
+  if ((ssize_t) nbyte < 0)
+    abort ();
+
   while ((rtnval = read (fildes, buf, nbyte)) == -1
         && (errno == EINTR))
     QUIT;
@@ -1837,13 +1845,17 @@
 }
 
 ssize_t
-emacs_write (int fildes, const char *buf, ssize_t nbyte)
+emacs_write (int fildes, const char *buf, size_t nbyte)
 {
   register ssize_t rtnval, bytes_written;
 
+  /* Defend against negative NBYTE, as in emacs_read.  */
+  if ((ssize_t) nbyte < 0)
+    abort ();
+
   bytes_written = 0;
 
-  while (nbyte > 0)
+  while (nbyte != 0)
     {
       rtnval = write (fildes, buf, nbyte);