wp_tempnam() recursive broken code

[cloudware]

ref. ​https://wordpress.org/support/topic/unable-to-update-plugins-after-upgrade-to-42?replies=11#post-6871167

see [31936]

"If the folder is falsey, use it's (sic) parent directory name instead"

this self-calling function is broken when wordpress requires maintenance mode to be set... calling wp_tempnam("/.maintenance",""); recurses until PHP fatally runs out of memory.

[hnle]

suggested by taka2 (​https://ja.forums.wordpress.org/topic/150570)

[SergeyBiryukov]

#32123 was marked as a duplicate.

[cloudware]

I have a concern with this patch - if the purpose of using a temporary name of '/.maintenance' is so WordPress can prevent access to a site under maintenance, then use of a continuously variable number instead surely isn't good.

Purely as an observation and admittedly not knowing of the inner workings, I don't know why a tempname function need to be so complex?

[Monika]

if I'm using AddHandler php56-cgi .php /htaccess
this bug doesn't appear,

I know this is a work around but maybe it is helpfully

[pattyland]

#32162 was marked as a duplicate.

[taka2]

This problem is very serious because it affects also Wordpress self updating, not only plugin/thema updating.

Wordpress's "wp_tempnam" function is not supposed that argument $filename is root directory and has no basename (such as "/.maintenance").
If $filename has no basename(extensions only), wp_tempname is called recursively to generate tempname based on the parent directory of $filename,
but parent of root directory("/") is also root("/"), so it causes infinite recursive calling.

Wordpress updater creates ".maintenance" file to the installed directory,
therefore this problem occurs when the following conditions.
. Updating via FTP (ftpsock or ftpext).
. Wordpress is installed at the root directory of FTP server (using chrooted account).

In this case, Wordpress updater calls function wp_tempnam('/.maintenance'), so it falls into infinite loop.
If Wordpress is installed at subdirectory of FTP home, or if updating via ssh or direct, this problem will not occur.

[SergeyBiryukov]

#32164 was marked as a duplicate.

[dd32]

In 32322:

When creating a temporary file treat the / directory properly, to prevent it ending up in an endless self-calling loop.
Props hnle, taka2. Fixes #32135. See #31811

[dd32]

In 32324:

When creating a temporary file treat the / directory properly, to prevent it ending up in an endless self-calling loop.
Props hnle, taka2. Fixes #32135. See #31811
Merges [32322] to the 4.2 branch.