From: Linus Torvalds <email@example.com> To: Steven Rostedt <firstname.lastname@example.org> Cc: Kees Cook <email@example.com>, Anna-Maria Gleixner <firstname.lastname@example.org>, Linux Kernel Mailing List <email@example.com>, tcharding <firstname.lastname@example.org> Subject: Re: Hashed pointer issues Date: Mon, 30 Apr 2018 16:57:36 +0000 [thread overview] Message-ID: <CA+55aFzpJC4+tuSopeze72D2sv1urGdap8+Bj2Y9hEYitAkE4Q@mail.gmail.com> (raw) In-Reply-To: <email@example.com> On Mon, Apr 30, 2018 at 9:41 AM Steven Rostedt <firstname.lastname@example.org> wrote: > > > > And if we really want a command line option, can we make that still hash > > the pointer, just force the entropy early. That way kernel developers that > > test that command line option are still testing the *hashing*, they just > > are missing the good entropy. > That may work too. Even with bad entropy, pointers at start up are hard > to come by, and I can't see a hacker being able to use them as it only > happens once during boot. No, if people use the command line option, *all* pointers - not just the boot-time ones - would get cryptographically bad hashes, since you don't want to change the hash once it's picked (because then you couldn't use the hashing to identify objects). So the boot command line wouldn't affect just the bootup hashing, it would be bad at runtime too. But at least a person booting with that option would get the same *behavior* as everybody else, and they wouldn't be testing something fundamnetally different (it's still hashing, just not cryptographically strong). Although in *practice* we'd have tons of entropy on any modern development CPU too, since any new hardware will have the hardware random number generation. Some overly cautious person might not trust it, of course. Linus
next prev parent reply other threads:[~2018-04-30 16:57 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-04-30 15:50 Anna-Maria Gleixner 2018-04-30 16:11 ` Kees Cook 2018-04-30 16:31 ` Linus Torvalds 2018-04-30 16:41 ` Steven Rostedt 2018-04-30 16:57 ` Linus Torvalds [this message] 2018-04-30 17:01 ` Linus Torvalds 2018-04-30 17:06 ` Randy Dunlap 2018-04-30 17:12 ` Linus Torvalds 2018-05-01 7:05 ` tcharding 2018-05-03 8:41 ` Geert Uytterhoeven 2018-04-30 18:38 ` Kees Cook 2018-04-30 19:00 ` Linus Torvalds 2018-04-30 19:16 ` Kees Cook 2018-04-30 20:01 ` Linus Torvalds 2018-04-30 20:07 ` Linus Torvalds 2018-04-30 21:23 ` Tobin C. Harding
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