Messages in this thread | | | Date | Fri, 7 Jan 2005 20:12:55 -0200 | From | Marcelo Tosatti <> | Subject | Re: uselib() & 2.6.X? |
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On Fri, Jan 07, 2005 at 04:15:28PM -0800, Linus Torvalds wrote: > > > On Fri, 7 Jan 2005, Alan Cox wrote: > > > > Please don't use that for mainline - do_brk_locked doesn't follow kernel > > convention > > I agree, I also find the "do_brk_locked()" naming confusing. To me it > implies that we already _are_ locked, not that we're going to lock. > > On the other hand, I think Alan's patch is equally confusing: the calling > rules for "do_brk()" and "do_mmap()" are the same, and they are "caller > takes mmap_sem". > > So I think you _both_ broke kernel conventions. > > So I'd personally much prefer to just first fix the bug minimally (by just > taking the lock in the two places that need it), and then _separately_ say > "we should warn if anybody ever calls 'do_brk()' without the lock". That's > how we tend to verify locking in other cases, ie we have things like > > if (!spin_is_locked(&t->sighand->siglock)) > BUG(); > > to verify the calling conventions. Same would go for mmap_sem (although we > don't seem to have any "sem_is_writelocked()" test - although you can fake > it with > > if (down_read_trylock(&mm->mmap_sem)) > BUG(); > > instead. > > Now _that_ is a non-silent failure mode. The machine doesn't just silently > deadlock: it tells you exactly what's wrong.
Only problem is that current do_brk() callers dont take the lock - you would need a version of do_brk() that doesnt warn for them?
But yes, the warning is better than silent failure or security problem for out-of-the tree users. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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