LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Stephan Mueller <smueller@chronox.de>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Daniel Borkmann <dborkman@redhat.com>,
	"'Quentin Gouchet'" <quentin.gouchet@gmail.com>,
	"'LKML'" <linux-kernel@vger.kernel.org>,
	linux-crypto@vger.kernel.org, linux-api@vger.kernel.org,
	Neil Horman <nhorman@tuxdriver.com>
Subject: Re: [PATCH v11 1/2] crypto: AF_ALG: add AEAD support
Date: Mon, 26 Jan 2015 05:26:33 +0100	[thread overview]
Message-ID: <1526868.qaVuSjCOn7@tachyon.chronox.de> (raw)
In-Reply-To: <20150125235550.GB18212@gondor.apana.org.au>

Am Montag, 26. Januar 2015, 10:55:50 schrieb Herbert Xu:

Hi Herbert,

> On Wed, Jan 21, 2015 at 02:19:17AM +0100, Stephan Mueller wrote:
> > +		/* use the existing memory in an allocated page */
> > +		if (ctx->merge) {
> > +			sg = sgl->sg + sgl->cur - 1;
> > +			len = min_t(unsigned long, len,
> > +				    PAGE_SIZE - sg->offset - sg->length);
> > +			err = memcpy_from_msg(page_address(sg_page(sg)) +
> > +					      sg->offset + sg->length,
> > +					      msg, len);
> > +			if (err)
> > +				goto unlock;
> > +
> > +			sg->length += len;
> > +			ctx->merge = (sg->offset + sg->length) &
> > +				     (PAGE_SIZE - 1);
> > +
> > +			ctx->used += len;
> > +			copied += len;
> > +			size -= len;
> 
> Need to add a continue here to recheck size != 0.

Why would that be needed?

When size is still != 0 (i.e. the existing buffer is completely filled, we 
have still some remaining data), we fall through to the while loop that 
generates a new buffer.

If we add a continue here, we start the next iteration in the outer while loop 
which again checks for the merging of data in an existing buffer. As this 
merging will never happen as we filled that buffer completely in the previous 
loop, we always will fall through to the inner while loop. Thus, not having 
the check for size != 0 is functional identical to having it (besides, it is 
more efficient to not having it). 

Note, this case is triggered in my tests, where I use sendmsg with first a 
small buffer, followed by a large buffer. And I still can send 65536 bytes to 
the kernel.

-- 
Ciao
Stephan

  reply	other threads:[~2015-01-26  4:26 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-21  1:18 [PATCH v11 0/2] crypto: AF_ALG: add AEAD and RNG support Stephan Mueller
2015-01-21  1:19 ` [PATCH v11 1/2] crypto: AF_ALG: add AEAD support Stephan Mueller
2015-01-25 23:54   ` Herbert Xu
2015-01-25 23:55   ` Herbert Xu
2015-01-26  4:26     ` Stephan Mueller [this message]
2015-01-26  4:32       ` Herbert Xu
2015-01-26  4:39         ` Stephan Mueller
2015-01-26  4:41           ` Herbert Xu
2015-01-25 23:59   ` Herbert Xu
2015-01-26  0:06   ` Herbert Xu
2015-01-26  4:35     ` Stephan Mueller
2015-01-26  4:37       ` Herbert Xu
2015-01-26  4:40         ` Stephan Mueller
2015-01-21  1:19 ` [PATCH v11 2/2] crypto: AF_ALG: enable AEAD interface compilation Stephan Mueller

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1526868.qaVuSjCOn7@tachyon.chronox.de \
    --to=smueller@chronox.de \
    --cc=dborkman@redhat.com \
    --cc=herbert@gondor.apana.org.au \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-crypto@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=nhorman@tuxdriver.com \
    --cc=quentin.gouchet@gmail.com \
    --subject='Re: [PATCH v11 1/2] crypto: AF_ALG: add AEAD support' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).