Detecting a stack overflow
The following program uses the
preprocessor macro ALLOCATION_SIZE to specify at compile time how many bytes will be written in the function
write_buffer to a buffer allocated on the stack in the function
func:
//
// TODO: See https://github.com/google/sanitizers/wiki/AddressSanitizer
//
#include <stdio.h>
int write_buffer(char* buf, unsigned int size) {
for (unsigned int pos=0; pos < size; pos++) {
buf[pos] = (char) pos;
}
}
int func() {
char buf[20];
write_buffer(buf, ALLOCATION_SIZE); // Uh, oh.
return 42;
}
int main() {
printf("ALLOCATION_SIZE = %d\n", ALLOCATION_SIZE);
printf("func returned %d\n", func());
printf("\n\n");
}
Because the size of the buffer is limited to 20 bytes, the program exhibits a stack overflow if ALLOCATION_SIZE is greater than 20.
Makefile
This Makefile creates two programs, prog-ok where ALLOCATION_SIZE is set to 20 and prog-stack-overflow where ALLOCATION_SIZE is set to 21, and runs them.
.PHONY: run
run: prog-ok prog-stack-overflow
./prog-ok
./prog-stack-overflow
prog-ok: prog.c
gcc -DALLOCATION_SIZE=20 -fsanitize=address $< -o $@
prog-stack-overflow: prog.c
gcc -DALLOCATION_SIZE=21 -fsanitize=address $< -o $@
Because -fsanitize=address is set, it is possible to determine where the stack overflow took place.