The security cookie must be initialized immediately on entry to an EXE or DLL. The /GS compiler option requires that the security cookie be initialized before any function that uses the cookie is run. The fifth statement declares a structure whose size on an x86 platform is not more than 8 bytes. The third and fourth statements declare arrays whose size is too small. The first two declarations contain elements of pointer type. However, the following statements do not declare GS buffers. A GS buffer can be one of these:Īn array that is larger than 4 bytes, has more than two elements, and has an element type that is not a pointer type.Ī data structure whose size is more than 8 bytes and contains no pointers.Ī buffer allocated by using the _alloca function.Īny class or structure that contains a GS buffer.įor example, the following statements declare GS buffers. GS BuffersĪ buffer overrun security check is performed on a GS buffer.

If a different value is detected, the process is terminated. A different value indicates that an overwrite of the stack may have occurred. On function exit, and during frame unwinding on 64-bit operating systems, a helper function is called to make sure that the value of the cookie is still the same. On function entry, the allocated space is loaded with a security cookie that is computed once at module load. On functions that the compiler recognizes as subject to buffer overrun problems, the compiler allocates space on the stack before the return address. For more information about suppressing buffer overrun detection, see safebuffers. If you expect your application to have no security exposure, use /GS. Causing a buffer overrun is a technique used by hackers to exploit code that does not enforce buffer size restrictions. Detects some buffer overruns that overwrite a function's return address, exception handler address, or certain types of parameters.

Assembly stack smashing detected