Messages in this thread | | | Date | Mon, 25 Aug 2014 11:51:47 -0700 (PDT) | From | Hugh Dickins <> | Subject | Re: [PATCH 1/1] ipc/shm: fix the historical/wrong mm->start_stack check |
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On Mon, 25 Aug 2014, Oleg Nesterov wrote: > On 08/25, Hugh Dickins wrote: > > > And I think I'll let Linus's guard page justify your 4 (to match comment) > > in place of the original's mysterious 5. > > Ah, thanks again. Yes, if we want to guarantee 4 pages we should check 5. > > Although obviously this doesn't explain the original's 5, this was > written before check_stack_guard_page().
I meant, you changed the coded 5 to 4, to match the comment above it; and if I were insistent on maximizing back-compatible-safety, I would say that 4 should go back to 5; but since Linus added the guard page gap at next->vm_start in between, I don't mind if you stick with 4 there to match the comment.
Disclaimer: I may be mistaken in each clause of that paragraph, and you may prefer to ignore everything I wrote there as worthless! But I didn't understand your "to guarantee 4 we should check 5".
Hugh
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