Supreme leader mad

Is there some lore about this I don't know?

There is no C++ allowed in the Linux kernel and Linus has gone on several major rants about how terrible a language it is.
- Is it all C?
Torvalds just really dislikes C++. He's gone on the record saying that he thinks it's just not a good language. In his own words "C++ is just a waste, there is no design at all, just adding some scum on top of C."
- he's not wrong
Linus is a C advocate btw, which make him even more goated
”C++ is a horrible language. It's made more horrible by the fact that a lot of substandard programmers use it, to the point where it's much much easier to generate total and utter crap with it. Quite frankly, even if the choice of C were to do nothing but keep the C++ programmers out, that in itself would be a huge reason to use C.”
http://harmful.cat-v.org/software/c++/linus

A PHP kernel?

The day I learned that Linus shares my disdain for all things OOP was such a good day for me.

He is is OK with OOP. The Linux kernel is full of OPP C, but he doesn't like C++
I feel the OOP debate got a bit out of hand. I hate OOP as well, as a paradigm.
But I love objects. An object is just a struct that can perform operations on itself. It's super useful. So many problems lend themselves to the use of objects.
I've been writing a mix of C and C++ for so long I don't even know where the line is supposed to be. It's "C with objects". I probably use only 1% of the functionality of C++, but that 1% is a huge upgrade from bare C IMO.
- Agreed. Objects are nice and a great way to program. Composition is great. Traits/interfaces are great. Namespaces are great. Objects are a really nice way to reap the benefits of principles like these.
  But then there are aspects of OOP that absolutely suck, like inheritance. I hate inheritance. The rules get very confusing very quickly. For example, try understanding overriding of methods. Do I need to call the superclass method or not? If not, does it get called automatically? If so, in what order? How do these rules change for the constructor? Now repeat this exercise for every OOP language you use and try not to mix them up... Java, C++, Python, etc.
  Fortunately, it feels like we rely on inheritance less and less these days. As an example, I really like how Java allows you to implement Runnable these days. Before, if you wanted to run a thread, you needed a separate object that inherited Thread. And what if that object needs to inherit from another one too? Things would get out of hand quickly. (This is a very old example, but with lambdas and other new features, things are getting even better now.)
  Anyway, long story short, I think OOP is a complicated way to achieve good principles, and there are simpler ways to achieve those principles than a full OOP implementation.
Me, when Linus' opinion is different to mine: "Linus has such weirdly strong opinions about this"
Me when Linus' opinion is the same as mine: VINDICATION

What's wrong with c++?

For kernel dev it would be a disaster, there's too much implicit action, and abstractions that have unknown runtime cost. The classic answer is that everyone uses 10% of its features over C, but nobody can agree on which 10%.
As someone forced to get up to date with C++ recently, at this point it's a language in full identity crisis. It wants so badly to be Rust, but it's got decades of baggage it's dragging along.