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Date: Thu, 26 May 2011 17:14:49 -0700 From: Kees Cook <kees.cook@...onical.com> To: David Miller <davem@...emloft.net> Cc: eric.dumazet@...il.com, joe@...ches.com, mingo@...e.hu, akpm@...ux-foundation.org, netdev@...r.kernel.org, drosenberg@...curity.com, a.p.zijlstra@...llo.nl, eparis@...isplace.org, eugeneteo@...nel.org, jmorris@...ei.org, tgraf@...radead.org Subject: Re: [patch 1/1] net: convert %p usage to %pK On Wed, May 25, 2011 at 09:50:40PM -0400, David Miller wrote: > From: Kees Cook <kees.cook@...onical.com> > Date: Wed, 25 May 2011 16:29:21 -0700 > > > Hi David, > > > > On Tue, May 24, 2011 at 03:58:01AM -0400, David Miller wrote: > >> From: Eric Dumazet <eric.dumazet@...il.com> > >> Date: Tue, 24 May 2011 09:45:01 +0200 > >> > >> > Le mardi 24 mai 2011 à 00:35 -0700, Joe Perches a écrit : > >> > > >> >> I think it's be better without the casts > >> >> using the standard kernel.h macros. > >> >> > >> >> void *ptr; > >> >> > >> >> ptr = maybe_hide_ptr(sk); > >> >> r->id.idiag_cookie[0] = lower_32_bits(ptr); > >> >> r->id.idiag_cookie[1] = upper_32_bits(ptr); > >> >> > >> > > >> > I am not sure I want to patch lower_32_bits() and upper_32_bits() for > >> > this. > >> > > >> > They dont work on pointers, but on "numbers", according to kerneldoc > >> > Andrew wrote years ago. gcc agrees : > >> > > >> > net/ipv4/inet_diag.c: In function ‘inet_csk_diag_fill’: > >> > net/ipv4/inet_diag.c:119: warning: cast from pointer to integer of different size > >> > net/ipv4/inet_diag.c:120: error: invalid operands to binary >> > >> > make[1]: *** [net/ipv4/inet_diag.o] Error 1 > >> > >> Also you can't do this, the "cookie" is used by the kernel future > >> lookups to find sockets. > >> > >> The kernel pointer is part of the API, so sorry you can't "hide" > >> kernel pointers in this case without really breaking user visible > >> things. > > > > But this is precisely what we're trying to control with kptr_restrict. > > Setting kptr_restrict will make inet_diag (and some details of similar > > things in /proc) meaningless. Based on the name, "diag" isn't going to be > > used in normal operation, and kptr_restrict is 0 by default, so only system > > owners interested in this will enable it and effectively disable inet_diag. > > Are you kidding me? > > inet_diag is the standard way to dump sockets using netlink. > It's not a special obscure debugging facility, it's for real > users. > > And the encoded kernel pointer here is used as a shortcut to looking > up precise sockets. We got this dropped from the /proc view; why can't we do the same for this netlink interface? -Kees -- Kees Cook Ubuntu Security Team -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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