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    SubjectRe: [PATCH] [RESEND] PIE executable randomization
    On Wed, Aug 08, 2007 at 04:03:07PM +0200, Jiri Kosina wrote:
    > @@ -870,11 +917,15 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
    > * default mmap base, as well as whatever program they
    > * might try to exec. This is because the brk will
    > * follow the loader, and is not movable. */
    > +#ifdef CONFIG_X86
    > + load_bias = 0;
    > +#else
    > load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
    > +#endif
    > }
    >
    > error = elf_map(bprm->file, load_bias + vaddr, elf_ppnt,
    > - elf_prot, elf_flags);
    > + elf_prot, elf_flags,0);
    > if (BAD_ADDR(error)) {
    > send_sig(SIGKILL, current, 0);
    > retval = IS_ERR((void *)error) ?

    If I'm reading the above hunk correctly, this means we will randomize
    all PIEs and even all dynamic linkers invoked as executables on i?86 and
    x86_64, and on the rest of arches we won't randomize at all, instead
    load ET_DYN objects at ELF_ET_DYN_BASE address.

    But I don't see anything i?86/x86_64 specific on this.

    What would make much more sense to me would be conditionalizing on
    whether we are loading a dynamic linker (in which case loading it
    at ELF_ET_DYN_BASE is desirable or not (PIEs, ...; and for PIEs we
    want to randomize on all architectures).

    So something like
    if (elf_interpreter)
    load_bias = 0;
    else
    /* Probably dynamic linker invoked as
    /lib*/ld*so* program args - load at
    ELF_ET_DYN_BASE. */
    load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
    instead of
    #ifdef CONFIG_X86
    load_bias = 0;
    #else
    load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
    #endif

    Jakub
    -
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