Bug #78326 [Com]: improper memory deallocation on stream_get_contents() with fixed lenght buffer

Edit report at https://bugs.php.net/bug.php?id=78326&edit=1 ID: 78326 Comment by: albertcasademont at gmail dot com Reported by: albertcasademont at gmail dot com Summary: improper memory deallocation on stream_get_contents() with fixed lenght buffer Status: Open Type: Bug Package: Streams related Operating System: Alpine Linux 3.10 PHP Version: 7.2.21RC1 Block user comment: N Private report: N New Comment: PR: https://github.com/php/php-src/pull/4464 Previous Comments: ------------------------------------------------------------------------ [2019-07-23 12:02:01] albertcasademont at gmail dot com Description: ------------ When calling stream_get_contents() with a fixed length buffer, the memory allocated for that buffer is not freed even though the actual data might be much shorter than the allocated buffer. This can potentially crash the script just after a couple of stream_get_contents() calls due to memory issues. If we don't specify a fixed lenght buffer, php will correctly reallocate the string to the exact amount of data read. This would also be the expected thing to do even if we fix the buffer length. Test script: --------------- <?php $f = tmpfile(); fwrite($f, '.'); $chunks = array(); for ($i = 0; $i < 1000; ++$i) { rewind($f); $chunks[] = stream_get_contents($f, 1000000); } var_dump(count($chunks)); Expected result: ---------------- int(1000) Actual result: -------------- Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 1003520 bytes) in /in/HP2U9 on line 9 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=78326&edit=1