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A buffer overflow; A stack overflow; Attempting to execute a program that does not compile correctly. (Some compilers [which?] will output an executable file despite the presence of compile-time errors.) In C code, segmentation faults most often occur because of errors in pointer use, particularly in C dynamic memory allocation.
A NOP-sled is the oldest and most widely known technique for exploiting stack buffer overflows. [2] It solves the problem of finding the exact address of the buffer by effectively increasing the size of the target area. To do this, much larger sections of the stack are corrupted with the no-op machine instruction.
Canaries or canary words or stack cookies are known values that are placed between a buffer and control data on the stack to monitor buffer overflows. When the buffer overflows, the first data to be corrupted will usually be the canary, and a failed verification of the canary data will therefore alert of an overflow, which can then be handled, for example, by invalidating the corrupted data.
A 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 .
Visualization of a software buffer overflow. Data is written into A, but is too large to fit within A, so it overflows into B.. In programming and information security, a buffer overflow or buffer overrun is an anomaly whereby a program writes data to a buffer beyond the buffer's allocated memory, overwriting adjacent memory locations.
Opcode for aseq 0x40,gr1,gr1, an instruction that asserts that the stack register is equal to itself. [3] ARM A32: NOP: 4 0x00000000 This stands for andeq r0, r0, r0. The assembly instruction nop will most likely expand to mov r0, r0 which is encoded 0xE1A00000 (little-endian architecture). [4] ARM T32 (16 bit) NOP: 2 0xb000
Convert to an int8 (on the stack as int32) and throw an exception on overflow. Base instruction 0x82 conv.ovf.i1.un: Convert unsigned to an int8 (on the stack as int32) and throw an exception on overflow. Base instruction 0xB5 conv.ovf.i2: Convert to an int16 (on the stack as int32) and throw an exception on overflow. Base instruction 0x83 conv ...
For example, in the tiny model CS=DS=SS, that is the program's code, data, and stack are all contained within a single 64 KB segment. In the small memory model DS=SS, so both data and stack reside in the same segment; CS points to a different code segment of up to 64 KB.