Bug (informatique)

vignette|upright=1|Le Mac triste : écran indiquant un code erreur sur les premières versions du MacIntosh d'Apple. En informatique, un bug (prononcé en français : ) ou bogue est un défaut de conception d'un programme informatique à l'origine d'un dysfonctionnement. La gravité du dysfonctionnement peut aller de bénigne, causant par exemple des défauts d'affichage mineurs à majeure, tels un plantage du système pouvant entraîner de graves accidents, par exemple la destruction en vol de la première fusée Ariane 5, en 1996. Un bug peut résider dans une application, dans les logiciels tiers utilisés par cette application, voire dans le firmware d'un composant matériel comme ce fut le cas du bug de la division du Pentium. Un patch est un morceau de logiciel destiné à corriger un ou plusieurs bugs. Description Les bugs sont une des causes de dysfonctionnement des appareils informatiques ; parmi les autres causes de dysfonctionnement, on trouve : *Les erreurs de manipulation, le

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Preventing Use-After-Free Attacks with Fast Forward Allocation

Sanidhya Kashyap, Jungwon Lim

Memory-unsafe languages are widely used to implement critical systems like kernels and browsers, leading to thousands of memory safety issues every year. A use-after-free bug is a temporal memory error where the program accidentally visits a freed memory location. Recent studies show that use-after-free is one of the most exploited memory vulnerabilities. Unfortunately, previous efforts to mitigate use-after-free bugs are not widely deployed in real-world programs due to either inadequate accuracy or high performance overhead. In this paper, we propose to resurrect the idea of one-time allocation (OTA) and provide a practical implementation with efficient execution and moderate memory overhead. With one-time allocation, the memory manager always returns a distinct memory address for each request. Since memory locations are not reused, attackers cannot reclaim freed objects, and thus cannot exploit use-after-free bugs. We utilize two techniques to render OTA practical: batch page management and the fusion of bump-pointer and fixed-size bins memory allocation styles. Batch page management helps reduce the number of system calls which negatively impact performance, while blending the two allocation methods mitigates the memory overhead and fragmentation issues. We implemented a prototype, called FFmalloc, to demonstrate our techniques. We evaluated FFmalloc on widely used benchmarks and real-world large programs. FFmalloc successfully blocked all tested use-after-free attacks while introducing moderate overhead. The results show that OTA can be a strong and practical solution to thwart use-after-free threats.

USENIX ASSOC2021

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NrOS: Effective Replication and Sharing in an Operating System

Ankit Bhardwaj, Sanidhya Kashyap

Writing a correct operating system kernel is notoriously hard. Kernel code requires manual memory management and type-unsafe code and must efficiently handle complex, asynchronous events. In addition, increasing CPU core counts further complicate kernel development. Typically, monolithic kernels share state across cores and rely on one-off synchronization patterns that are specialized for each kernel structure or subsystem. Hence, kernel developers are constantly refining synchronization within OS kernels to improve scalability at the risk of introducing subtle bugs. We present NrOS, a new OS kernel with a safer approach to synchronization that runs many POSIX programs. NrOS is primarily constructed as a simple, sequential kernel with no concurrency, making it easier to develop and reason about its correctness. This kernel is scaled across NUMA nodes using node replication, a scheme inspired by state machine replication in distributed systems. NrOS replicates kernel state on each NUMA node and uses operation logs to maintain strong consistency between replicas. Cores can safely and concurrently read from their local kernel replica, eliminating remote NUMA accesses. Our evaluation shows that NrOS scales to 96 cores with performance that nearly always dominates Linux at scale, in some cases by orders of magnitude, while retaining much of the simplicity of a sequential kernel.

USENIX ASSOC2021

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Troubleshooting Blackbox SON Control Software with Minimal Causal Sequences

Sam David Whitlock

Software bugs are inevitable in software-defined networking control software, and troubleshooting is a tedious, time-consuming task. In this paper we discuss how to improve control software troubleshooting by presenting a technique for automatically identifying a minimal sequence of inputs responsible for triggering a given bug, without making assumptions about the language or instrumentation of the software under test. We apply our technique to five open source SDN control platforms Floodlight, NOX, PDX, Pyretic, ONOS and illustrate how the minimal causal sequences our system found aided the troubleshooting process.

Assoc Computing Machinery2014

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Logiciel

thumb|Démarche de construction d'un logiciel. En informatique, un logiciel est un ensemble de séquences d’instructions interprétables par une machine et d’un jeu de données nécessaires à ces opératio

Programmation informatique

vignette|Liste d'instructions sur le Commodore 64 La programmation, appelée aussi codage dans le domaine informatique, désigne l'ensemble des activités qui permettent l'écriture des programmes inform

Langage de programmation

thumb|Fragment de code écrit dans le langage de programmation JavaScript. Un langage de programmation est un langage informatique destiné à formuler des algorithmes et produire des programmes informa

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This course focuses on software security fundamentals, secure coding guidelines and principles, and advanced software security concepts. Students learn to assess and understand threats, learn how to design and implement secure software systems, and get hands-on experience with security pitfalls.

CS-487: Industrial automation

This course consists of two parts:

architecture of automation systems, hands-on lab
handling of faults and failures in real-time systems, including fault-tolerant computing

EE-530: Test of VLSI systems

Test of VLSI Systems covers theoretical knowledge related to the major algorithms used in VLSI test, and design for test techniques. Basic knowledge related to computer-aided design for test techniques, and their integration into a design-flow are presented.