On Wed, 11 Apr 2007 17:22:57 +1000 Nick Piggin <[EMAIL PROTECTED]> wrote:
> Eric Dumazet wrote: > > On Sat, 07 Apr 2007 19:30:14 +1000 > > Nick Piggin <[EMAIL PROTECTED]> wrote: > > > > > >>Eric Dumazet wrote: > > > > > > > >>>- Current mm code have a problem with 64bit futexes, as spoted by Nick : > >>> > >>>get_futex_key() does a check against sizeof(u32) regardless of futex being > >>>64bits or not. > >>>So it is possible a 64bit futex spans two pages of memory... > >>>I had to change get_futex_key() prototype to be able to do a correct test. > >> > >>I wonder if it should be encfocing alignment to keep in on 1 page? > > > > > > I believe I just did that :) > > Yes :P What I was trying to say before jumping on a plane is that > sys_futex/sys_futex64 calls should each check their own address alignment, so > the deeper parts of the call stack always know alignment is correct. > > This will remove all the fsize you pass around, and also sanitise the > userspace > argument much higher in the call stack, which is very preferable and more > conventional. > > Maybe this isn't possible (it's very obvious, so there may be a good reason it > hasn't been done). I had this idea as well, but considering get_futex_key() is exported in include/linux/futex.h, I believe some out-of tree thing is using it. As this external thing certainly is not doing the check itself, to be on the safe side we should enforce it in get_futex_key(). I agree with you : If we want to maximize performance, we could say : The check *must* be done by the caller. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
