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[2001-07-18 06:07 UTC] brueckner at respublica dot de
When using ob_start() with a script included via auto_prepend_file and then doing something like this:
ob_start("my_flush");
function my_flush($buffer)
{
$buffer = preg_replace("/(<!--REPLACE\\s.*?-->)/e", "parse(\"\\1\")",
$buffer);
return $buffer;
}
PHP 4.0.6 SIGSEGV's with this message in the error_log:
[Wed Jul 18 11:55:08 2001] Script: '/home/htdocs/test.php'
---------------------------------------
output.c(235) : Block 0x0824C940 status:
Beginning: Overrun (magic=0x08294990, expected=0x7312F8DC)
End: Unknown
---------------------------------------
./zend_execute.c(334) : Freeing 0x082A8CB4 (28131 bytes), script=/home/htdocs/test.php
zend_variables.c(117) : Actual location (location was relayed)
[Wed Jul 18 11:55:08 2001] [notice] child pid 30192 exit signal Segmentation fault (11)
If I replace the line
$buffer = preg_replace("/(<!--REPLACE\\s.*?-->)/e", "parse(\"\\1\")",
$buffer);
with
$newbuffer = preg_replace("/(<!--REPLACE\\s.*?-->)/e", "parse(\"\\1\")",
$buffer);
it works fine.
Any ideas for a fix?
Harry
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Last updated: Tue Oct 28 04:00:01 2025 UTC |
Easy one to fix :) <?php ob_start("my_flush"); function my_flush($buffer) { $buffer = preg_replace("/(<!--REPLACE\\s.*?-->)/e", "parse(\"\\1\")", $buffer); return $buffer; } ?> /home/yohgaki/public_html/bugs/12227/bug.php(9) : Warning - String is not zero-terminated (ZZZZZZZZZZZZZZAnyone who are interested in this problem. here is a patch for this problem. This should solve unwanted free for this specific case. Question is do we really want this? Index: main/output.c =================================================================== RCS file: /repository/php4/main/output.c,v retrieving revision 1.84 diff -u -r1.84 output.c --- main/output.c 7 Feb 2002 02:50:28 -0000 1.84 +++ main/output.c 7 Feb 2002 06:31:35 -0000 @@ -164,7 +164,7 @@ ALLOC_INIT_ZVAL(orig_buffer); ZVAL_STRINGL(orig_buffer, OG(active_ob_buffer).buffer, OG(active_ob_buffer).text_length, 0); orig_buffer->refcount=2; /* don't let call_user_function() destroy our buffer */ - orig_buffer->is_ref=1; + orig_buffer->is_ref=0; ALLOC_INIT_ZVAL(z_status); ZVAL_LONG(z_status, status);Last patch that I memtioned still have problem with simple output handler like ob_handler($buffer) { $result = $buffer; return $result; } This could happen easily when user conditinally convert buffer.... To fix this segfualt completely, it seems I have to copy buffer before pass it to user defined output handler.the following testcase even crashes PHP4. it seems if you assign a value to the given parameter (here $s) which is larger than the original, it will crash. copying the input into a seperate variable and work with that is a workaround. still this simple buffer overflow ought to be easy to fix? using 4.1.1 (build dec 30, 2001): ob_start( "handler" ); function handler( $s ) { $s = $s."foobar foobar foobar"; return $s; }