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Bug #28396 crash when memory limit reached
Submitted: 2004-05-14 13:23 UTC Modified: 2004-05-14 17:08 UTC
Votes:11
Avg. Score:5.0 ± 0.0
Reproduced:8 of 9 (88.9%)
Same Version:3 (37.5%)
Same OS:3 (37.5%)
From: operator at infomaniak dot ch Assigned:
Status: Not a bug Package: Reproducible crash
PHP Version: 4.3.6 OS: linux glibc 2.2
Private report: No CVE-ID: None
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 [2004-05-14 13:23 UTC] operator at infomaniak dot ch 
Description:
------------
When memory limit is reached, this irremdiably cause a 
segfault. 
-- 
php with no extensions at all compiled with: 
    --disable-all \ 
    --with-apxs=/usr/sbin/apxs \ 
    --enable-sigchild \ 
    --disable-ipv6 \ 
    --enable-memory-limit \ 
    --with-config-file-path=/etc/httpd \ 
    --disable-static \ 
    --enable-shared \ 
    --enable-debug 
 
reproductible with any memory_limit value (tried from 512 
bytes to 8M) 

Reproduce code:
---------------
<?
$i=1;
while($i++) {
        $a .= ".";
        if (($i % 1024) == 0) {
                echo memory_get_usage() . "<br/>\n";
                flush();
        }
}
?>


Expected result:
----------------
some kind of "memory exhausted" message 

Actual result:
--------------
apache thread segfault

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 [2004-05-14 13:46 UTC] wez@php.net 
This is expected behaviour; in a debug build, when memory allocation fails, we force a segfault.

Don't run debug builds in production.
 [2004-05-14 14:05 UTC] operator at infomaniak dot ch 
Alright. This is not true. 
Memory allocation failing due to external bad behaviour 
must cause segfault, not because of memory_limit reached. 
 
Then, I get exactly the same result without 
--enable-debug . 
 
For info, crash occurs exactly when memory_limit is 
reached. 
 
(output just before crash: 
509528 
510552 
511576 
with a memory limit at 512000 
output got without --enable-debug) 
)
 [2004-05-14 15:33 UTC] iliaa@php.net 
No crashes here and memory analysis tools show no 
suspicious operations.
 [2004-05-14 16:41 UTC] operator at infomaniak dot ch 
Have you really tried to put this script and run it 
with a php_admin_value memory_limit 512000  
?
 [2004-05-14 17:05 UTC] operator at infomaniak dot ch 
Finaly, this won't segfault, you were right. 
Then, it appears that in some rare conditions, just after 
memory_limit reached, segfault comes. 
But, this may be because of any other extension. 
 
For this, could you tell how to compile seperate 
extensions 
(ala phpize etc...) with debug enabled ? 
with a core compiled with --enable-debug, extensions still 
get build without debug...
 [2004-05-14 17:08 UTC] iliaa@php.net 
yes
 
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