Error: dynamic-stack-buffer-overflow

Address Sanitizer Error: dynamic-stack-buffer-overflow

This example shows the error that results from a buffer access outside the bounds of a stack-allocated object.

Example - alloca overflow (right)

// example1.cpp
// dynamic-stack-buffer-overflow error
#include <malloc.h>

__declspec(noinline)
void foo(int index, int len) {

    volatile char *str = (volatile char *)_alloca(len);

    //    reinterpret_cast<long>(str) & 31L;

    str[index] = '1'; // Boom !
}

int main(int argc, char **argv) {

    foo(33, 10);
    return 0;
}

To build and test this example, run these commands in a Visual Studio 2019 version 16.9 or later developer command prompt:

cl example1.cpp /fsanitize=address /Zi
devenv /debugexe example1.exe

Resulting error

Example - alloca overflow (left)

// example2.cpp
// dynamic-stack-buffer-overflow error
#include <malloc.h>

__declspec(noinline)
void foo(int index, int len) {

    volatile char *str = (volatile char *)_alloca(len);

    str[index] = '1';  // Boom!
}

int main(int argc, char **argv) {
    foo(-1, 10);
    return 0;
}

To build and test this example, run these commands in a Visual Studio 2019 version 16.9 or later developer command prompt:

cl example2.cpp /fsanitize=address /Zi
devenv /debugexe example2.exe

Resulting error - alloca overflow (left)

Example - several calls to alloca

// example3.cpp
// dynamic-stack-buffer-overflow error
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>

#define SIZE 7
extern void nothing();
int x=13,*aa,*bb,y=0;
int fail = 0;
int tmp;

int main()
{
    int* cc;
    int i;
    int k = 17;
    __try {
        tmp = k;
        aa = (int*)_alloca(SIZE * sizeof(int));
        if (((int)aa) & 0x3)
            fail = 1;
        for (i = 0; i < SIZE; i++) {
            aa[i] = x + 1 + i;
        }
        bb = (int*)_alloca(x * sizeof(int));
        if (((int)bb) & 0x3)
            fail = 1;

        for (i = 0; i < x; i++) {
            bb[i] = 7;
            bb[i] = bb[i] + i;
        }
        {
            int s = 112728283;
            int ar[8];
            for (i = 0; i < 8; i++)
                ar[i] = s * 17 * i;
        }

        cc = (int*)_alloca(x);
        if (((int)cc) & 0x3)
            fail = 1;

        cc[0] = 0;
        cc[1] = 1;
        cc[2] = 2;
        cc[3] = 3;             // <--- Boom!
        for (i = 0; i < x; i++)
            if (bb[i] != (7 + i))
                fail = 1;
        if (tmp != k)
            fail = 1;
        if (fail) {
            printf("fail\n");
            exit(7);
        }
        printf("%d\n", (*cc) / y);
        printf("fail\n");
        exit(7);
    }
    __except (1)
    {
        for (i = 0; i < SIZE; i++)
            if (aa[i] != (x + i + 1))
                fail = 1;
        if (fail) {
            printf("fail\n");
            exit(7);
        }
        printf("pass\n");
        exit(0);
    }
}

To build and test this example, run these commands in a Visual Studio 2019 version 16.9 or later developer command prompt:

cl example3.cpp /fsanitize=address /Zi
devenv /debugexe example3.exe

Resulting error - several calls to alloca

See also

AddressSanitizer overview
AddressSanitizer known issues
AddressSanitizer build and language reference
AddressSanitizer runtime reference
AddressSanitizer shadow bytes
AddressSanitizer cloud or distributed testing
AddressSanitizer debugger integration
AddressSanitizer error examples