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Fresh from the notebook

Tech 17 Sep 2026 6 min read

Write Combining Merges Adjacent Stores Before Memory Traffic

Some memory regions are written far more often than they are read. Frame buffers, device apertures, and streaming output areas are common examples. Sending every small CPU store as a separate memory transaction can waste bus bandwidth and transaction overhead. Write combining gives the processor a temporary place to collect compatible stores. Several writes targeting nearby addresses can be merged into a larger transaction before they leave the CPU. The technique favors sustained write throughput, but it changes the timing and ordering properties that software can safely assume.

CPU Memory

Cybersecurity 17 Sep 2026 5 min read

Userfaultfd Moves Page-Fault Resolution Into Userspace

Userfaultfd Moves Page-Fault Resolution Into Userspace A thread touches a registered virtual-memory page and stops before the access completes. Instead of resolving the fault entirely inside the kernel, Linux can report the event through a userfaultfd and let another userspace component decide when and with what content execution may continue. That design supports live migration, post-copy memory transfer, checkpointing, and related memory-management systems, but it also places a concurrency-sensitive decision point outside the faulting thread.

Cybersecurity Linux Security

Artificial Intelligence 17 Sep 2026 6 min read

Use Selective Classification to Trade Coverage for Error Rate

A classifier usually returns a label for every input, even when its score distribution is nearly tied or the input sits far from familiar data. Selective classification changes that interface: the system may return a prediction or abstain. The acceptance rule then determines both how many inputs receive predictions and how often those accepted predictions are wrong. This is not the same as making the classifier intrinsically more accurate. Abstention moves some cases out of the automatic-decision set. Its value depends on whether the selection score ranks difficult cases well enough for rejected inputs to contain a disproportionate share of errors.

Artificial Intelligence Classification

Linux 17 Sep 2026 4 min read

Truncating a Mapped File Can Trigger SIGBUS

A process can retain a valid mmap() address range after another operation shrinks the backing file, then receive SIGBUS when it touches a mapped page past the file’s new end. The mapping itself has not vanished. Its backing object no longer covers every page that the virtual mapping originally referenced. This boundary is easy to miss because mapping lifetime and file size are separate state. Closing the original file descriptor does not invalidate an established mapping, and shrinking the file does not act like munmap() on every process that maps it.

Linux mmap

Cybersecurity 17 Sep 2026 7 min read

TLS Must-Staple Turns Missing OCSP Evidence Into Handshake Failure

TLS Must-Staple Turns Missing OCSP Evidence Into Handshake Failure A TLS server can hold a valid private key and present a certificate that chains to a trusted root while its revocation evidence is unavailable. Ordinary OCSP stapling does not necessarily turn that absence into failure: a client can request status information, yet the server is permitted to omit a response in the base stapling protocol. That optionality creates a security boundary. An active intermediary that can suppress access to an OCSP responder can exploit client policies that accept an inconclusive revocation check. The TLS Feature extension defined by RFC 7633 changes the certificate itself so that selected TLS features become conditions of acceptable use. For OCSP stapling, the certificate can assert that a conforming client must receive the requested status evidence.

Cybersecurity TLS

Cybersecurity 17 Sep 2026 6 min read

TLS 1.3 Early Data Trades a Round Trip for Replay Exposure

TLS 1.3 Early Data Trades a Round Trip for Replay Exposure A returning TLS 1.3 client can possess a resumption ticket and application data ready to send before a new handshake has finished. Early data, commonly called 0-RTT data, permits those bytes to travel in the client’s first flight. The latency benefit changes a security property at exactly the point where an application may be tempted to act: early data does not carry the same replay protection as ordinary post-handshake application data.

Cybersecurity TLS 1.3

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