Sending data in a signal

The well-known kill system call has been around for decades and is used to send a signal to another process. The most common use is to terminate or kill another process by sending the KILL or TERM signal but it can be used for a form of IPC, usually around giving the other process a “kick” to do something.

One thing that isn’t as well known is besides sending a signal to a process, you can send some data to it. This can either be an integer or a pointer and uses similar semantics to the known kill and signal handler. I came across this when there was a merge request for procps. The main changes are using sigqueue instead of kill in the sender and using a signal action not a signal handler in the receiver.

Read more Sending data in a signal

WordPress 5.4

Debian packages for WordPress version 5.4 will be uploaded shortly. I’m just going through the install testing now.

One problem I have noticed is, at least for my setup, there is an issue with network updates. The problem is that WordPress will ask me if I want to update the network sites, I say yes and get a SSL error.

After lots of debugging, the problem is that the fsockopen option to use SNI is turned off for network updates. My sites need SNI so without this they just bomb out with a SSL handshake error.

I’m not sure what the real fix is, but my work-around was to temporary set the SNI in the fsockopen transport while doing the site updates.

The file you want wp-includes/Requests/Transport/fsockopen.php and in the request method of Requests_Transport_fsockopen you’ll see something like:

                       stream_context_set_option($context, array('ssl' => $context_options)); 
                else { 
                        $remote_socket = 'tcp://' . $host; 

Just before the stream_context_set_option put the line:

                        $context_options['SNI_enabled'] = true;

Ugly but it works

Update May 2020

Looking into this more, there is a bug in the fsockopen transport. If you have verify_peer turned off (which network upgrades do) then it turns SNI off. You still need SNI even if you are going to not verify the certificate. I raised but its simply commenting out the line that disables SNI in Requests/Transport/fsockopen.php around line 444.

procps-ng 3.3.16

procps-ng version 3.3.16 was released today. Besides some documentation and library updates, there were a few incremental changes.

Zombie Hunting with pgrep

Ever wanted to find zombies? Perhaps processes with other states? pgrep has a shiny new runstate flag to help you which will match process against the runstate. I’m curious to see the use-cases for this flag; it certainly will get used (e.g. find my zombies) but as some processes bounce in and out of states (think Run to Sleep and back) it might add some confusion.

Snice plays nice with PIDs

Speaking of ancient corpses, snice was not matching against PIDs. The best use for snice is to not use it (as the man page says) but some people do and some people noticed it never matched against PIDs.
The issue was reading the process state up to 128 bytes, but process state lines are always longer than 128 bytes so a bounds check failed and it skipped that PID (and every other PID too).

Top Enhancements

Top got a bunch of love again in this release. If you ever wanted your processes to be shown in fuchsia? Perhaps goldenrod? With some earlier versions of top, you could by directly editing the toprc file but now everyone can have more than the standard 8 colours!

If you use the other filters parameter for some fancy process filtering in top, it now will save that configuration.

Collapsed children (process names are weird) get some help. If you are in tree view, you can collapse or fold the children processes under the parent. Their CPU is also added to the parent so there are no “missing” CPU ticks.

For people who use the One True Editor (which is, of course, VIM) you can use the vim navigation keys to move through the process list.

Where to find it?

You’ll find the latest version of procps either at our git repository or download a tarball.

WordPress 5.2.4

Hot on the heels of WordPress version 5.2.3 which fixed a bunch of stuff we have WordPress 5.2.4 with fixes for six security issues.

There is a certain trick to matching up what the WordPress Blog thinks has been fixed and the changsets between the old version and the new. The curious thing is there were 6 changsets backported to older versions of WordPress, so you might think “six issues, six changesets, what’s the problem?”. The problem is that two of them fix the same thing (or one sort-of fixed it and the second really did) and another I couldn’t link to any vulnerability, BUT it was to do with directory traversal issue.

The hardest part of maintaining the Debian WordPress packages is the backporting. Trying to link the changes to the bugs is next to impossible so I generally import all the ones they have in the specific major version and hope for the best. This isn’t ideal, but information about what the actual bugs are and how they are fixed is not forthcoming.

WordPress 5.1.1

The Debian packages for WordPress version 5.1.1 are being updated as I write this. This is a security fix for WordPress that stops comments causing a cross-site scripting bug. It’s an important one to update.

The backports should happen soon so even if you are using Debian stable you’ll be covered.