(__getcwd_chk): Always fail if the buffer is too small.

debug/getcwd_chk.c

@@ -24,8 +24,8 @@
 char *
 __getcwd_chk (char *buf, size_t size, size_t buflen)
 {
-  char *res = __getcwd (buf, MIN (size, buflen));
-  if (res == NULL && errno == ERANGE && size > buflen)
+  if (size > buflen)
     __chk_fail ();
-  return res;
+
+  return __getcwd (buf, size);
 }

debug/pread64_chk.c

@@ -23,11 +23,8 @@
 ssize_t
 __pread64_chk (int fd, void *buf, size_t nbytes, off64_t offset, size_t buflen)
 {
-  /* In case NBYTES is greater than BUFLEN, we read BUFLEN+1 bytes.
-     This might overflow the buffer but the damage is reduced to just
-     one byte.  And the program will terminate right away.  */
-  ssize_t n = __pread64 (fd, buf, offset, MIN (nbytes, buflen + 1));
-  if (n > 0 && (size_t) n > buflen)
+  if (nbytes > buflen)
     __chk_fail ();
-  return n;
+
+  return __pread64 (fd, buf, offset, MIN (nbytes, buflen + 1));
 }

debug/readlink_chk.c

@@ -27,15 +27,12 @@
 ssize_t
 __readlink_chk (const char *path, void *buf, size_t len, size_t buflen)
 {
-  /* In case LEN is greater than BUFLEN, we read BUFLEN+1 bytes.
-     This might overflow the buffer but the damage is reduced to just
-     one byte.  And the program will terminate right away.  */
+  if (len > buflen)
+    __chk_fail ();
+
 #ifdef HAVE_INLINED_SYSCALLS
-  int n = INLINE_SYSCALL (readlink, 3, path, buf, MIN (len, buflen + 1));
+  return INLINE_SYSCALL (readlink, 3, path, buf, MIN (len, buflen + 1));
 #else
-  int n = __readlink (path, buf, MIN (len, buflen + 1));
+  return __readlink (path, buf, MIN (len, buflen + 1));
 #endif
-  if (n > 0 && (size_t) n > buflen)
-    __chk_fail ();
-  return n;
 }