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

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Message-ID: <cxspxz5jeiigd34cl7x3asyx4lowefjpffj3ip4mwpxdwh34e6@xzpqbmlihbcg>
Date: Sun, 23 Feb 2025 12:12:47 +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 10:52), Herbert Xu wrote:
> On Sun, Feb 23, 2025 at 11:09:32AM +0900, Sergey Senozhatsky wrote:
> >
> > Right, for lzo/lzo-rle we need a safety page.
> 
> We should fix it because it's a security hole for anyone who calls
> it through the Crypto API.

Yeah, I don't disagree.

> > 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;
> > 	}
> > }
> 
> Z_OK is actually an error, see crypto/deflate.c:

I saw Z_STREAM_END, but deflate states "this is not an error" and
there are more places like this.

> 	ret = zlib_deflate(stream, Z_FINISH);
> 	if (ret != Z_STREAM_END) {
> 		ret = -EINVAL;
> 		goto out;
> 	}
> 
> We could change this to ENOSPC for consistency.

So it will ENOSPC all errors, not sure how good that is.  We also
have lz4/lz4hc that return the number of bytes "(((char *)op) - dest)"
if successful and 0 otherwise.  So any error is 0. dst_buf overrun
is also 0, impossible to tell the difference, again not sure if we
can just ENOSPC.