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    SubjectRe: + c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-update-after-mm- num_exe_file_vmas-removal.patch added to -mm tree
    Oleg Nesterov wrote:
    > On 04/20, Cyrill Gorcunov wrote:
    >> Guys, while I more-less agree with Matt about single-shot behaviour
    >> [ let me copy my and his email
    >> >> With mm->exe_file this prctl option become a one-shot
    >> >> only, and while at moment our user-space tool can perfectly
    >> >> live with that I thought that there is no strict need to
    >> >> limit the option this way from the very beginning.
    >> >>
    >> > As far as backward compatibility, isn't it better to lift that restriction
    >> > later rather than add it? I think the latter would very likely "break"
    >> > things whereas the former would not.
    >> >
    >> > I also prefer that restriction because it establishes a bound on how
    >> > frequently the symlink can change. Keeping it a one-shot deal makes the
    >> > values that show up in tools like top more reliable for admins.
    >> ]
    >> I guess maybe it's time to drop one-shot requirement and as result
    >> we can drop MMF_EXE_FILE_CHANGED bit completely,
    > Plus perhaps we can remove this for_each_vma check?
    >> making overall code
    >> simplier?
    > Personally I'd certainly prefer this ;)
    > But let me repeat to avoid the confusion. I am fine either way,
    > I am not going to discuss this again unless I see something which
    > looks technically wrong. And the current MMF_EXE_FILE_CHANGED
    > doesn't look right even if the problem is minor.

    Yeah, whole this protection does not protect anything and can be easily bypassed.
    For example task can re-execute itself and change exe-file again and again.

    > Oleg.

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