lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 17 Oct 2022 21:45:08 +0200 From: Ard Biesheuvel <ardb@...nel.org> To: Kees Cook <keescook@...omium.org> Cc: "Guilherme G. Piccoli" <gpiccoli@...lia.com>, Anton Vorontsov <anton@...msg.org>, Colin Cross <ccross@...roid.com>, Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH] pstore: migrate to crypto acomp interface (take 2) On Mon, 17 Oct 2022 at 21:40, Kees Cook <keescook@...omium.org> wrote: > > On Mon, Oct 17, 2022 at 09:33:06PM +0200, Ard Biesheuvel wrote: > > On Mon, 17 Oct 2022 at 21:29, Kees Cook <keescook@...omium.org> wrote: > > > > > > On Mon, Oct 17, 2022 at 08:14:14PM +0200, Ard Biesheuvel wrote: > > > > So once we use the same size for input and output, I was curious > > > > whether we could encrypt in place, and get rid of the big_oops_buf. > > > > And the answer is 'yes', precisely because we have this horrid per-CPU > > > > allocation which serves as a bounce buffer. And this is not specific > > > > to acomp, the old comp algorithms get wrapped in scomps which receive > > > > the same treatment. > > > > > > Ah, in the sense that "in place" is actually happening in the per-cpu > > > allocation, and only if it succeeds does the input buffer get > > > overwritten? > > > > Something like that IIRC. > > > > > > So at that point, I wondered what the point is of all this complexity. > > > > Do we really need 6 different algorithms to compress a couple of K of > > > > ASCII text on a code path that is ice cold by definition? Wouldn't it > > > > be better to drop the crypto API altogether here, and just use GZIP > > > > via the library interface? > > > > > > Well, my goal was to make the algo "pstore doesn't care". If someone > > > picks deflate, do they still get all the per-cpu allocations? > > > > > > > Not if you use the library interface directly. > > > > The issue with the percpu buffers is that they are only kept if any > > scomp TFMs are active, but this is always the case for pstore, as you > > don't want to allocate it on the panic path. > > Okay, so strictly speaking, eliminating the per-CPU allocation is an > improvement. Keeping scomp and doing in-place compression will let > pstore use "any" compressions method. > I'm not following the point you are making here. > Is there a crypto API that does _not_ preallocate the per-CPU stuff? > Because, as you say, it's a huge amount of memory on the bigger > systems... > The library interface for each of the respective algorithms.
Powered by blists - more mailing lists