Note that focusing stacking doesn’t require fancy equipment, either you can focus stack with a standard camera (even a smartphone camera, in fact), though I do recommend you work with a tripod and a manual focus lens if you can, as I discuss in a moment. You blend the images to achieve a final file that features a sharp foreground, a sharp middleground, and a sharp background.You take several images of a scene, making sure to focus on each part (i.e., the foreground, the middleground, and the background).While the concepts may sound tricky, the basic process is very simple: For other uses, see Stack overflow (disambiguation).Feeling confused? Don’t be. In software, a stack buffer overflow or stack buffer overrun occurs when a program writes to a memory address on the program's call stack outside of the intended data structure, which is usually a fixed-length buffer. Stack buffer overflow bugs are caused when a program writes more data to a buffer located on the stack than what is actually allocated for that buffer. This almost always results in corruption of adjacent data on the stack, and in cases where the overflow was triggered by mistake, will often cause the program to crash or operate incorrectly. Stack buffer overflow is a type of the more general programming malfunction known as buffer overflow (or buffer overrun). Overfilling a buffer on the stack is more likely to derail program execution than overfilling a buffer on the heap because the stack contains the return addresses for all active function calls.Ī stack buffer overflow can be caused deliberately as part of an attack known as stack smashing. If the affected program is running with special privileges, or accepts data from untrusted network hosts (e.g. a webserver) then the bug is a potential security vulnerability. If the stack buffer is filled with data supplied from an untrusted user then that user can corrupt the stack in such a way as to inject executable code into the running program and take control of the process. This is one of the oldest and more reliable methods for attackers to gain unauthorized access to a computer. #include #include void foo ( char * bar ) Platform-related differences Ī number of platforms have subtle differences in their implementation of the call stack that can affect the way a stack buffer overflow exploit will work. Some machine architectures store the top-level return address of the call stack in a register. This means that any overwritten return address will not be used until a later unwinding of the call stack. Another example of a machine-specific detail that can affect the choice of exploitation techniques is the fact that most RISC-style machine architectures will not allow unaligned access to memory. #Turn off movie effects stacking code#Ĭombined with a fixed length for machine opcodes, this machine limitation can make the technique of jumping to the stack almost impossible to implement (with the one exception being when the program actually contains the unlikely code to explicitly jump to the stack register). Within the topic of stack buffer overflows, an often-discussed-but-rarely-seen architecture is one in which the stack grows in the opposite direction. This change in architecture is frequently suggested as a solution to the stack buffer overflow problem because any overflow of a stack buffer that occurs within the same stack frame cannot overwrite the return pointer.
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