Microsoft has contributed thousands of lines of code to the Linux kernel, the open source software at the heart of the widely used Linux operating system. And now, the software giant has contributed some controversy too.

Sometime over the past few years, as Microsoft beefed up the Linux kernel with code related to its Hyper-V virtualization software, one unidentified developer needed a name for a piece of code used by the software, and for some unknown reason, he went with this: 0x__B16B00B5__.

That's hexspeak for "Big Boobs."

Red Hat kernel developer Matthew Garrett is not impressed. "At the most basic level, it's just straightforward childish humour," he wrote on his blog. "But it's also specifically male childish humour. Puerile sniggering at breasts contributes to the continuing impression that software development is a boys club where girls aren't welcome."

Microsoft apologized for the "offensive string" on Friday. "We have submitted a patch to fix this issue and the change will be published in a future release of the kernel," the company said in an e-mailed statement.

That patch could cause trouble for developers who use Microsoft's Azure cloud platform, which is based on Hyper-V, Garrett said in his blog post. "It's especially irritating in this case because Azure may depend on this constant, so changing it will break things," he wrote. "So, full marks, Microsoft. You've managed to make the kernel more offensive to half the population and you've made it awkward for us to rectify it."

Microsoft has become a big-time contributor to Linux as it tries to make its VMware-alternative, Hyper-V, a legitimate platform for Linux applications. Hyper-V is a way of running many virtual servers – machines that exist only as software – on a single physical server.

In April, the Linux Foundation said that after adding all that Hyper-V code to the kernel, Microsoft was one of the top 20 contributors to Linux. Developers there contributed 1 percent of the new Linux kernel code between October 2011 and January of this year, the Foundation said.

Microsoft developer K. Y. Srinivasan has contributed much of this Hyper-V code, though it's not clear who came up with Big Boobs. He didn't respond to messages Friday.

This story has been corrected to indicate that 0xB16B00B5 is hexspeak.