From: Tom Rix <trix@redhat.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: davem@davemloft.net, smueller@chronox.de,
linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] crypto: drbg: check blocklen is non zero
Date: Thu, 20 Aug 2020 06:27:36 -0700 [thread overview]
Message-ID: <97371bc7-ebb6-92f2-bbaa-6b444e27cb8b@redhat.com> (raw)
In-Reply-To: <20200820071522.GA21511@gondor.apana.org.au>
There are many divide by 0 reports. This one got attention because it is in crypto, where i believe problems, even false positives, should be fixed.
Tom
On 8/20/20 12:15 AM, Herbert Xu wrote:
> On Sun, Aug 02, 2020 at 10:12:47AM -0700, trix@redhat.com wrote:
>> From: Tom Rix <trix@redhat.com>
>>
>> Clang static analysis reports this error
>>
>> crypto/drbg.c:441:40: warning: Division by zero
>> padlen = (inputlen + sizeof(L_N) + 1) % (drbg_blocklen(drbg));
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
>>
>> When drbg_bocklen fails it returns 0.
>>
>> if (drbg && drbg->core)
>> return drbg->core->blocklen_bytes;
>> return 0;
> Yes but it can only fail if the drbg is not instantiated. If
> you're hitting the generate path with an uninstantiated drbg you've
> got bigger problems than a divide by zero.
>
> So how is this even possible?
>
> Cheers,
next prev parent reply other threads:[~2020-08-20 13:29 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-02 17:12 [PATCH] crypto: drbg: check blocklen is non zero trix
2020-08-02 18:29 ` Stephan Mueller
2020-08-20 7:15 ` Herbert Xu
2020-08-20 13:27 ` Tom Rix [this message]
2020-08-20 20:06 ` Herbert Xu
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=97371bc7-ebb6-92f2-bbaa-6b444e27cb8b@redhat.com \
--to=trix@redhat.com \
--cc=davem@davemloft.net \
--cc=herbert@gondor.apana.org.au \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=smueller@chronox.de \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox