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    SubjectRe: Patch 4/6 randomize the stack pointer

    > I actually just tried to paxtest a fresh Fedora Core 3, unadultered,
    > that I installed, and it FAILED every test. After a while, spender
    > reminded me about PT_GNU_STACK. It failed everything but the Executable
    > Stack test after execstack -c *. The randomization tests gave
    > 13(heap-etexec), 16(heap-etdyn), 17(stack), and none for main exec
    > (etexec,et_dyn) or shared library randomization.

    because you ran prelink.
    and you did not compile paxtest with -fPIE -pie to make it a PIE

    > Also, before you say it, I read, comprehended, and anylized the source.
    > This was PaXtest 0.9.6, and I did specific traces (after changing
    > body.c to prevent it from forking) to look for mprotect() and mmap()
    > calls and find out what they do (I saw probably glibc getting mmap()ed
    > in, there wasn't anything in the source doing the mmap() calls I saw).
    > There were no dirty tricks to mprotect() a high area of memory, which is
    > something Ingo called foul on in 0.9.5.

    there is one actually if you look careful enough.

    > if (strlen(a) > 4)
    > a[5] = '\0';
    > foo(a);
    > void foo(char *a) {
    > char b[5];
    > strcpy(b,a);
    > }
    > This code is safe, but you can't tell from looking at foo(). You don't
    > get a look at every other object being compiled against this one that
    > may call foo() either. So compile time buffer overflow detection is a
    > best-effort at best.

    actually this one gets caught, since this will be turned into a checking
    strcpy which aborts after the 5th character.

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