Bug #52312 [Bgs->Fbk]: PHP lstat problem

From: Date: Mon, 12 Jul 2010 16:03:54 +0000
Subject: Bug #52312 [Bgs->Fbk]: PHP lstat problem
References: 1  Groups: php.bugs 
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Edit report at http://bugs.php.net/bug.php?id=52312&edit=1

 ID:               52312
 Updated by:       pajoye@php.net
 Reported by:      v dot damore at gmail dot com
 Summary:          PHP lstat problem
-Status:           Bogus
+Status:           Feedback
 Type:             Bug
 Package:          Safe Mode/open_basedir
 Operating System: Linux
 PHP Version:      5.2.13

 New Comment:

Can you try with 5.3 please?


Previous Comments:
------------------------------------------------------------------------
[2010-07-12 17:51:24] v dot damore at gmail dot com

I tried again with a simple script test.php '<? echo "Ciao" ?>'
realpath_cache_size=1024k
realpath_cache_ttl=600

I have always same behavior (also second and following times I try to
call curl http://damorealt.xoom.it/test.php:

13692 chdir("/usr/local/myspace/webspace/httpdocs") = 0
13692 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
13692 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) =
0
13692 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
13692 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
13692 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
13692 lstat("/usr/local/myspace/webspace/httpdocs/test.php",
{st_mode=S_IFREG|0644, st_size=19, ...}) = 0
13692 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
13692 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) =
0
13692 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
13692 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
13692 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
13692 lstat("/usr/local/myspace/webspace/httpdocs/test.php",
{st_mode=S_IFREG|0644, st_size=19, ...}) = 0
13692 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
13692 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) =
0
13692 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
13692 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
13692 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
13692 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) =
0
13692 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
13692 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
13692 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
13692 lstat("/usr/local/myspace/webspace/httpdocs/test.php",
{st_mode=S_IFREG|0644, st_size=19, ...}) = 0
13692 open("/usr/local/myspace/webspace/httpdocs/test.php", O_RDONLY) =
16
13692 fstat(16, {st_mode=S_IFREG|0644, st_size=19, ...}) = 0
13692 read(16, "<? echo \"Ciao!\" ?>\n", 8192) = 19
13692 read(16, "", 8192)                = 0
13692 read(16, "", 8192)                = 0
13692 close(16)                         = 0
13692 chdir("/")                        = 0

------------------------------------------------------------------------
[2010-07-12 17:07:40] rasmus@php.net

phpinfo() is a special case.  Try it with a simple hello world script.

------------------------------------------------------------------------
[2010-07-12 16:56:36] v dot damore at gmail dot com

The real problem is that such full scan are repeated more then once:

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) =
0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

First check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) =
0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Second check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) =
0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0

Third check (incomplete)

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) =
0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096,
...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs",
{st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php",
{st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Final check and then read the file.

25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY)
= 16
25933 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 read(16, "<? phpinfo() ?>\n", 8192) = 16
25933 read(16, "", 8192)                = 0
25933 read(16, "", 8192)                = 0
25933 close(16)                         = 0

------------------------------------------------------------------------
[2010-07-12 16:35:46] pajoye@php.net

The scan of each element of the paths happen anyway, whether the paths
contain symlinks or not. Check the code TSRM/ for a deeper explanation.

------------------------------------------------------------------------
[2010-07-12 15:57:54] v dot damore at gmail dot com

@pajoye; as is described in "Actual result" part of this bug, first time
PHP engine check filepath there is a full scan of all directories at
least 4 
times before cache the result, this behavior anyway cannot scale in a so
large environment.

@rasmus: this is very interesting, I can consider upgrade to 5.3 in
order to avoid this behavior.

I know this is an extrema ratio: may I disable symlinks support from PHP
engine in order to avoid this behavior?

Is there an answer regarding the increase of realpath_cache_size
realpath_cache_ttl?

------------------------------------------------------------------------


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    http://bugs.php.net/bug.php?id=52312


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