linux-kernel - Re: [PATCH v5 02/12] crypto: acomp - Define new interfaces for compress/decompress batching.

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Message-ID: <u7t7gibspxu3lujdl4hambr72qd6o5u33udbojihngznlyistk@gmyyhwjuiwxc>
Date: Sun, 23 Feb 2025 11:09:32 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, 
	Barry Song <21cnbao@...il.com>, Yosry Ahmed <yosry.ahmed@...ux.dev>, 
	Minchan Kim <minchan@...nel.org>, "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, 
	"hannes@...xchg.org" <hannes@...xchg.org>, "nphamcs@...il.com" <nphamcs@...il.com>, 
	"chengming.zhou@...ux.dev" <chengming.zhou@...ux.dev>, "usamaarif642@...il.com" <usamaarif642@...il.com>, 
	"ryan.roberts@....com" <ryan.roberts@....com>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, 
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>, "davem@...emloft.net" <davem@...emloft.net>, 
	"clabbe@...libre.com" <clabbe@...libre.com>, "ardb@...nel.org" <ardb@...nel.org>, 
	"ebiggers@...gle.com" <ebiggers@...gle.com>, "surenb@...gle.com" <surenb@...gle.com>, 
	"Accardi, Kristen C" <kristen.c.accardi@...el.com>, "Feghali, Wajdi K" <wajdi.k.feghali@...el.com>, 
	"Gopal, Vinodh" <vinodh.gopal@...el.com>
Subject: Re: [PATCH v5 02/12] crypto: acomp - Define new interfaces for
 compress/decompress batching.

On (25/02/23 08:14), Herbert Xu wrote:
> On Sat, Feb 22, 2025 at 11:27:49PM +0900, Sergey Senozhatsky wrote:
> >
> > So I didn't look at all of them, but at least S/W lzo1 doesn't even
> > have a notion of max-output-len.  lzo1x_1_compress() accepts a pointer
> > to out_len which tells the size of output stream (the algorithm is free
> > to produce any), so there is no dst_buf overflow as far as lzo1 is
> > concerned.  Unless I'm missing something or misunderstanding your points.
> 
> I just looked at deflate/zstd and they seem to be doing the right
> things.
> 
> But yes lzo is a gaping security hole on the compression side.

Right, for lzo/lzo-rle we need a safety page.

It also seems that there is no common way of reporting dst_but overflow.
Some algos return -ENOSPC immediately, some don't return anything at all,
and deflate does it's own thing - there are these places where they see
they are out of out space but they Z_OK it

if (s->pending != 0) {
	flush_pending(strm);
	if (strm->avail_out == 0) {
		/* Since avail_out is 0, deflate will be called again with
		 * more output space, but possibly with both pending and
		 * avail_in equal to zero. There won't be anything to do,
		 * but this is not an error situation so make sure we
		 * return OK instead of BUF_ERROR at next call of deflate:
		 */
		s->last_flush = -1;
		return Z_OK;
	}
}