tac crashes with SIGBUS when input file is truncated during read · uutils/coreutils#9748

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U - tacgood first issuereported-canonical

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Beschreibung

Component

tac

Description

The tac utility crashes with "Bus error (core dumped)" when an input file is truncated while being read. This happens because tac uses memory-mapped I/O (mmap with MAP_SHARED) without installing a SIGBUS signal handler.

When a mapped file is truncated, subsequent access to the now-invalid memory region triggers SIGBUS. The SAFETY comments in the code acknowledge this behavior but treat process termination as acceptable. GNU tac handles this gracefully by avoiding direct memory mapping of untrusted input sources.

Test / Reproduction Steps

dd if=/dev/zero of=/tmp/tactest bs=1M count=10 2>/dev/null
(sleep 0.001; truncate -s 0 /tmp/tactest) &
tac /tmp/tactest

Impact

Denial of Service: This is particularly problematic for log rotation scenarios where tac might be reading logs that get truncated

Contributor Guide

Research-Richtung: Implementieren Sie einen SIGBUS Handler oder ersetzen Sie mmap durch read() bei abgeschnittenen Dateien. Verwenden Sie MAP PRIVATE, um Rückschreiben zu vermeiden, oder fallen Sie auf gepufferte E/A zurück.
Tech Stack: rust
Domain: cli
Issue Type: Fehler
Schwierigkeit: 3
Geschätzte Zeit: Halber Tag
Aktivitätsstatus: Aktiv
Klarheit: Klar
Voraussetzungen: Rustmmapsignal handling
Einsteigerfreundlichkeit: 55