wp_upload_dir() causing preg_match(): null byte in regex in wp-includes\functions.php on line 5163

[indextwo]

I initially submitted this to WooCommerce, as it initially appeared to be a big pertaining to its activation:

​https://github.com/woocommerce/woocommerce/issues/13008

However, upon basic testing, it looks like the issue is caused by the wp_upload_dir() function. For reference, this only seems to occur in a Win7 machine running XAMPP/Apache/PHP7. Testing remotely on nginx/PHP 5.6 and nginx/PHP7 LEMP CentOS servers, the issue doesn't appear (which leads me to believe it is a Windows issue).

To recreate:

function uploadDirTest() {
	echo '<pre style="padding-left: 10rem;">';
	print_r(wp_upload_dir());
	echo '</pre>';
}

add_action('admin_head', 'uploadDirTest');

Results

preg_match(): null byte in regex in wp-includes\functions.php on line 5163

Call stack

#0  wp_is_stream() called at [C:\xampplite\htdocs\mysite\wp-includes\functions.php:1600]
#1  wp_mkdir_p() called at [C:\xampplite\htdocs\mysite\wp-includes\functions.php:1900]
#2  wp_upload_dir() called at [C:\xampplite\htdocs\mysite\wp-content\plugins\vnmAdmin\vnmAdmin.php:659]
#3  uploadDirTest() called at [C:\xampplite\htdocs\mysite\wp-includes\class-wp-hook.php:298]
#4  WP_Hook->apply_filters() called at [C:\xampplite\htdocs\mysite\wp-includes\class-wp-hook.php:323]
#5  WP_Hook->do_action() called at [C:\xampplite\htdocs\mysite\wp-includes\plugin.php:453]
#6  do_action() called at [C:\xampplite\htdocs\mysite\wp-admin\admin-header.php:142]
#7  require_once(C:\xampplite\htdocs\mysite\wp-admin\admin-header.php) called at [C:\xampplite\htdocs\mysite\wp-admin\plugins.php:422]

[indextwo]

Update

Haven't had time to really look into why this is happening on a Windows platform specifically, but I have found a fix:

As per this thread: ​http://stackoverflow.com/a/39603464/988246 I changed the return of wp_is_stream($path) to single quotes rather than double:

return preg_match( '!^$wrappers_re://!', $path ) === 1;

The linked SO post suggests to me that the $path parameter of wp_is_stream is being passed null byte(s), and preg_replace with double quotes (") is trying to parse them.

[SergeyBiryukov]

Hi @indextwo, welcome to Trac! Thanks for the report.

Replying to indextwo:

The linked SO post suggests to me that the $path parameter of wp_is_stream is being passed null byte(s), and preg_replace with double quotes (") is trying to parse them.

The regex here includes $wrappers_re though, not $path, and it should not contain any null bytes. I could not reproduce the issue on Windows 7 or 10 with Apache and PHP 7.

Could you put var_dump( $wrappers_re ); before that line and see what the result is?

On my install, it's (php|file|glob|data|http|ftp|zip|compress.zlib|https|ftps|phar).

[indextwo]

Hey @SergeyBiryukov

Well spotted - I hadn't even clocked that $path wasn't in the preg_replace - I just found a thing that fixed it and wiped my brow.

I've just done a var_dump and it looks like I'm getting the exact same result as you, with the exception of compress.bzip2:

string(78) "(php|file|glob|data|http|ftp|zip|compress.zlib|compress.bzip2|https|ftps|phar)"

...however, I've also just realised that the problem has mysteriously disappeared [insert embarrassed emoji here].

I thought it was super-odd that it appeared out of nowhere yesterday, but I assumed it might have been linked to the 4.7.2 update, which happened that morning for me. I'd tried restarting all of my services, but hadn't tried rebooting my actual computer.

It might still be worth noting that whatever caused a null byte to get into the function, using single quotes instead of the double in the regex completely solved it.

[huemanfoo]

Hi peeps,

i had this issue just now after installing and running a plugin called "Regenerate Thumbnails" (​https://wordpress.org/plugins/regenerate-thumbnails/)

Warning: preg_match(): Null byte in regex in functions.php on line 5219

I found that it was a permissions issue!

Navigated to the \wp-content\uploads folder and set the permissions correctly, this seemed to get rid of the error messages at least.

Hope this helps anyone in a similar situation :)

[MuninMunin]

Hello @huemanfoo , could you elaborate on how was it a permissions issue and how did you fix it? I do have the regenerate-thumbnails plugin since forever but never ran until this error until today, on my localhost only.

by the way, @indextwo looking for this error I ran into your posts many times, you were everywhere, I'm glad you fixed your problem.