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Bug #78538 shmop memory leak
Submitted: 2019-09-14 19:19 UTC Modified: 2019-09-15 11:03 UTC
From: ptk2003 at gmail dot com Assigned:
Status: Verified Package: *Extensibility Functions
PHP Version: 7.3.9 OS: Windows only
Private report: No CVE-ID: None
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 [2019-09-14 19:19 UTC] ptk2003 at gmail dot com
Description:
------------
shmop_open() with any parametrs add about 4KB apache.
"a", "c" irrelevant

for example this code add 4MegaByte working memory apache:
for($i=0; $i<1000; $i++){
$shmophsw=shmop_open(0x4051, "c", 0777, 65536);
shmop_close($shmophsw);
}//for

apache 2.4.41 x64
php-7.3.9-Win32-VC15-x64
windows 2016 server


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 [2019-09-14 19:49 UTC] danack@php.net
Can you give more indication of why you think this is classified as a memory leak, and not just normal memory usage for that extension?

The code below isn't calling https://www.php.net/manual/en/function.shmop-delete.php to free the memory, so it's not too surprising some is resident.

Also, 1000 * 65kb would be 65Mb if it was a memory leak. As you say it's only 4 MegaByte that sounds, like it's not leaking, just taking a bit more memory than you might expect.
 [2019-09-14 20:05 UTC] ptk2003 at gmail dot com
4KB memory independent of the size of allocated memory in "c" or "n" open mode

1000 interations $shmophsw=shmop_open(0x4051, "c", 0777, 1);
shmop_close($shmophsw); or shmop_open(0x4051, "c", 0777, 65536); give same result:
httpd.exe increase 4MB working ram.


shmop_delete() not change behaviour
(and how use shmop if delete segment after create?)

$shmophsw=shmop_open(0x4051, "a", 0, 0); give same behaviour: each add 4KB httpd.exe
 [2019-09-15 10:02 UTC] cmb@php.net
-Status: Open +Status: Verified -Operating System: windows server 2016 x64 +Operating System: Windows only
 [2019-09-15 10:02 UTC] cmb@php.net
This looks like a Windows only issue, and the culprit appears to
be that we're not unmapping the shm->descriptor if it's no longer
needed[1].

[1] <https://github.com/php/php-src/blob/php-7.3.9/TSRM/tsrm_win32.c#L731>
 [2019-09-15 11:03 UTC] ptk2003 at gmail dot com
it possible to fix in current or future version?
 
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