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    Subject[patch 30/47] exec: fix stack excutability without PT_GNU_STACK
    2.6.25-stable review patch.  If anyone has any objections, please let us
    know.

    ------------------
    From: Hugh Dickins <hugh@veritas.com>

    commit 96a8e13ed44e380fc2bb6c711d74d5ba698c00b2 upstream

    Kernel Bugzilla #11063 points out that on some architectures (e.g. x86_32)
    exec'ing an ELF without a PT_GNU_STACK program header should default to an
    executable stack; but this got broken by the unlimited argv feature because
    stack vma is now created before the right personality has been established:
    so breaking old binaries using nested function trampolines.

    Therefore re-evaluate VM_STACK_FLAGS in setup_arg_pages, where stack
    vm_flags used to be set, before the mprotect_fixup. Checking through
    our existing VM_flags, none would have changed since insert_vm_struct:
    so this seems safer than finding a way through the personality labyrinth.

    Reported-by: pageexec@freemail.hu
    Signed-off-by: Hugh Dickins <hugh@veritas.com>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/exec.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/fs/exec.c
    +++ b/fs/exec.c
    @@ -605,7 +605,7 @@ int setup_arg_pages(struct linux_binprm
    bprm->exec -= stack_shift;

    down_write(&mm->mmap_sem);
    - vm_flags = vma->vm_flags;
    + vm_flags = VM_STACK_FLAGS;

    /*
    * Adjust stack execute permissions; explicitly enable for
    --


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