Fix #81283: shmop can't read beyond 2147483647 bytes

`start`, `count` and `shmop->size` are `zend_long`, so we must not
restrict to `INT_MAX`.

Closes GH-7301.

Author: cmb69

NEWS

@@ -13,6 +13,9 @@ PHP                                                                        NEWS
 - CGI:
   . Fixed bug #80849 (HTTP Status header truncation). (cmb)
 
+- Shmop:
+  . Fixed bug #81283 (shmop can't read beyond 2147483647 bytes). (cmb, Nikita)
+
 - Standard:
   . Fixed bug #72146 (Integer overflow on substr_replace). (cmb)
   . Fixed bug #81265 (getimagesize returns 0 for 256px ICO images).

ext/shmop/shmop.c

@@ -251,7 +251,7 @@ PHP_FUNCTION(shmop_read)
 		RETURN_FALSE;
 	}
 
-	if (count < 0 || start > (INT_MAX - count) || start + count > shmop->size) {
+	if (count < 0 || start > (ZEND_LONG_MAX - count) || start + count > shmop->size) {
 		php_error_docref(NULL, E_WARNING, "count is out of range");
 		RETURN_FALSE;
 	}