Messages in this thread | | | Date | Thu, 8 Mar 2012 23:25:04 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file v3 |
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On Thu, Mar 08, 2012 at 08:05:34PM +0100, Oleg Nesterov wrote: ... > > > > Yes, exactly, I need to remove old mappings first (because VMAs > > we're about to restore may intersect with current map the host > > program has). And yes, once they all are removed I don't have > > /proc/pid/exe anymore. That's why I need num_exe_file_vmas == 0 > > case. > > OK, in this case PR_SET_MM_EXE_FILE should probably fail if > mm->num_exe_file_vmas != 0 ? This way it would be more or less > consistent or at least understandable. Just we add the new > special case: num_exe_file_vmas == 0 but exe_file != NULL > because c/r people are crazy. >
Sure, I can drop num_exe_file_vmas != 0 case and refuse to setup new exe symlink if there some VM_EXECUTABLE remains unmapped. Sounds good?
> > > And I don't think the unconditional > > > > > > down_write(&mm->mmap_sem); > > > set_mm_exe_file(mm, exe_file); > > > up_write(&mm->mmap_sem); > > > > > > is 100% right, this clears ->num_exe_file_vmas. This means that > > > (if you still have the old mapping) the new exe_file can go away > > > after added_exe_file_vma() + removed_exe_file_vma(). Normally this > > > should happen, but afaics this is possible. Note that even, say, > > > mprotect() can trigger added_exe_file_vma(). > > > > > > > Wait, Oleg, I'm confused, in case if there *is* exitsting VM_EXECUTABLEs > > then we jump into first banch and simply replace old exe_file. > > Yes. And then later you remove the old mapping (which do not match > the new file anyway) and the new exe_file goes away. Unlikely you > want this.
Yes, unlikely ;)
Cyrill
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