While a crashing program cannot immediately be called ‘healthy,’ in terms of backtracing/debugging, this is what a ‘healthy’ backtrace looks like:
Generally speaking, when we look at a backtrace, it will have a clear flow of functions which were called. Suddenly, variable and function names may be mangled, and a backtrace (the flow of functions the computer took to arrive at a given function that crashed and (in our example) smashed the stack) does not make sense anymore. Whereas technically a reference to ‘broken functions’ may not be fully correct, i.e., there is likely only one broken function, and there may even be no broken function when there is an external attack or malfunctioning program, it is a great way to think about a smashed stack. Each tile offset is a function nested deeper – more on broken functions in the next section. The analogy works because, just as all tiles are now broken in our fictive memory image, a smashed stack will result in ‘broken functions’ if you will. In terms of the tiles example above, imagine someone with a hammer hitting the first tile a little too hard and thereby smashing all the other tiles. In simplified terms, picture if one of those variables had a length of 10 characters, and some other function accidentally wrote 100 characters to that variable. C and C++ are two programming languages that use the stack extensively.Įach of these functions in the C/C++ program will have a name and likely a set of incoming variables and outgoing variables. The most basic function is on the bottom, and could be for example the main() function in a C or C++ program. Picture that each stacked tile is a function in the computer program. If each tile were a little offset from the previous one, it would be a better image, and we will soon see why. This is quite a good representation of a computer stack, with a few modifications. Start by imagining a stack of bathroom tiles stacked up, ready to be used by a tiler.
#STACK SMASHING DETECTED TROUBLESHOOTING SOFTWARE#
Generally speaking, a stack refers to a program processing stack, a stack of functions as defined in a given software program/code. So what is a stack? This, too, is a loosely defined term. The two most prominent issues which can cause stack smashing are 1) to write/over-allocate too much data in a given part of the stack, thereby overwriting another part of the stack, and 2) where some external source (malicious or not) overwrote another program’s stack, though this is much less common. Stack smashing is a somewhat loosely defined term that may point to various issues and can come from a variety of sources. Stack smashing can happen involuntarily – for example, when the developer introduced a bug that caused stack smashing – or maliciously – an attacker somehow trying to overflow or corrupt the stack of a program.
As a user, when you learn about stack smashing, the damage is likely done already. It is relatively easy (as in ‘somewhat easy’) for a developer to make a mistake that introduces stack smashing. As a developer, one will likely discover this term even earlier, especially if one has introduced a bug into the code, which causes a smashed stack. Working as a quality assurance engineer, one will sooner or later run into the term stack smashing. Learn what stack smashing is upfront and what can be done about it! What Is Stack Smashing? If your application has a serious issue that causes stack smashing, you’re in for a ride. Every minute of production downtime will generally cost a company money.
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