How Can You Use Polyspace Static Analysis to Avoid Buffer Overflows? And that is precisely what Polyspace static analysis does. An issue as subtle as this can be detected only if you can keep track of all execution paths in the program. In other words, a subset of execution paths exists where, despite the check, a buffer overflow can occur. The second check on the variable length is not performed at all.
The if block preceding the else if block performs an unrelated check on png_ptr->mode if that previous check fails, control goes outside the if - else if chain with just a warning. However, the snag here is that the check occurs in an else if block. Is exactly what is needed to avoid a buffer overflow when you use length.
BUFFER OVERFLOW CODE
If your program has sufficient privileges, this malicious code can take control of your application and lead to exploitation. An attacker can overflow your buffer precisely enough so that your program, instead of returning to the call site, jumps to the location of malicious code. This address is compromised because of the buffer overflow. The call stack also stores the address that the program jumps to when the called function returns. Area adjacent to the overflowing buffer stores return address of the function.You end up with unsafe and unreliable code. The corrupted value can also lead to a silent incorrect behavior - one that can escape detection. You can encounter the corrupted value causing a run-time error elsewhere in your code. The variable value is corrupted because of the buffer overflow. Area adjacent to the overflowing buffer stores another local variable or a function parameter.
When you call a function in your code, all data relevant to the call are stored in adjacent regions on the call stack. The severity of a buffer overflow depends on what is stored in the adjacent memory regions.
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