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    SubjectRe: [PATCH][RESEND] PIE randomization
    On Sat, Jul 07, 2007 at 02:13:01AM +0200, Jiri Kosina wrote:
    > On Thu, 5 Jul 2007, Rik van Riel wrote:
    >
    > > So the original patch has:
    > > #define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)
    > > For some reason(?) it got changed to the clearly buggy:
    > > #define BAD_ADDR(x) ((unsigned long)(x) >= PAGE_MASK)
    > > Jiri's patch undoes that second buggy define, which is very
    > > different from the original that was sent in by you and Ernie.
    >
    > This is a part of execshield patch, fthe pie-compiled binary executable
    > memory layout randomization was extracted from - see
    > http://people.redhat.com/~mingo/exec-shield/exec-shield-nx-2.6.19.patch
    >
    > Note that load_elf_interp() in vanilla kernel differs from the
    > execshield's (and pie-randomization.patch) version.
    >
    > The fix makes the BAD_ADDR check whether the address belongs to the
    > ERR_PTR range, which seems valid for all uses of BAD_ADDR in the patched
    > binfmt_elf.c (do_brk(), elf_map(), do_mmap() etc return valid address or
    > err ptr) ... am I missing something obvious here?

    I believe BAD_ADDR macro was changes from ((unsigned long)(x) >= TASK_SIZE)
    (which is the right test for invalid user addresses, stronger check than
    >= PAGE_MASK) to >= PAGE_MASK only because of the one check of the return
    value of load_elf_interp. All other uses of BAD_ADDR macro are either on
    userland addresses (what do_mmap, elf_map, do_brk etc. return;
    where TASK_SIZE or more is certainly wrong) or in one case still on unbiased
    ELF p_vaddr:
    if (BAD_ADDR(k) || elf_ppnt->p_filesz > elf_ppnt->p_memsz ||
    in load_elf_binary (where >= TASK_SIZE check is ok too).

    So perhaps doing this instead of changing BAD_ADDR to IS_ERR_VAL
    might be better:

    Signed-off-by: Jakub Jelinek <jakub@redhat.com>

    --- linux/fs/binfmt_elf.c 2007-06-08 21:53:45.000000000 +0200
    +++ linux/fs/binfmt_elf.c 2007-07-07 14:19:14.000000000 +0200
    @@ -80,7 +80,7 @@ static struct linux_binfmt elf_format =
    .hasvdso = 1
    };

    -#define BAD_ADDR(x) ((unsigned long)(x) >= PAGE_MASK)
    +#define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)

    static int set_brk(unsigned long start, unsigned long end)
    {
    @@ -1015,7 +1015,7 @@ static int load_elf_binary(struct linux_
    interpreter,
    &interp_map_addr,
    load_bias);
    - if (!BAD_ADDR(elf_entry)) {
    + if (!IS_ERR((void *)elf_entry)) {
    /* load_elf_interp() returns relocation adjustment */
    interp_load_addr = elf_entry;
    elf_entry += loc->interp_elf_ex.e_entry;

    Jakub
    -
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