Messages in this thread | | | Date | Tue, 6 Mar 2012 17:28:14 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 0/1] turn mm->exe_file into mm->exe_path |
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On 03/05, Matt Helsley wrote: > > On Mon, Mar 05, 2012 at 04:28:26PM +0100, Oleg Nesterov wrote: > > > > Unless there was another subtle reason, "struct path *exe_path" > > can equally work but it looks more clear. > > PATCH 1/1 looks fine. I think Alexey Dobriyan was working on a similar > patch years ago.
Good, can I take the above as your Acked-by/Reviewed-by ?
> > And can't we also remove added_exe_file_vma/removed_exe_file_vma? > > Why do we need mm->num_exe_file_vmas? Afaics it is only needed to > > "free" mm->exe_file if the application unmaps all these vmas. Say, > > to allow to unmount fs. > > Yup. I know it's not pretty to have to track the exe file refs this way > but I couldn't see any other way to keep a reference to the file (or > path) and avoid pinning the mounted filesystem the exectuable is on. > > > Can't we simply add PR_CLEAR_MM_EXE_PATH instead? Of course it is > > not enough if ->vm_file still has a reference. But c/r people want > > Relying solely on this prctl would break existing programs.
so we can't :/ I expected this answer.
> I believe Al > Viro's example was a program that copies its text to a new executable > area, unmaps the original, performs a pivot_root(), and finally umounts > the old root. Removing the counter would cause the mount to be pinned > for these programs and the umount would fail.
Yes, sure, the application should do PR_SET_MM_EXE_PATH(NULL) after unmap. I am wondering if there is any apllication which actually does this.
But OK, it is hardly possible to argue with "break existing program".
Thanks,
Oleg.
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