linux-kernel - Re: [PATCH v4 4/4] KEYS: Avoid false positive ENOMEM error on key read

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Message-ID: <e47bef56-9271-93e0-0e59-c77c253babea@redhat.com>
Date:   Wed, 18 Mar 2020 10:34:33 -0400
From:   Waiman Long <longman@...hat.com>
To:     David Howells <dhowells@...hat.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, netdev@...r.kernel.org,
        linux-afs@...ts.infradead.org, Sumit Garg <sumit.garg@...aro.org>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Roberto Sassu <roberto.sassu@...wei.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Chris von Recklinghausen <crecklin@...hat.com>
Subject: Re: [PATCH v4 4/4] KEYS: Avoid false positive ENOMEM error on key
 read

On 3/18/20 4:27 AM, David Howells wrote:
> Waiman Long <longman@...hat.com> wrote:
>
>> +static inline void __kvzfree(const void *addr, size_t len)
>> +{
>> +	if (addr) {
>> +		memset((void *)addr, 0, len);
>> +		kvfree(addr);
>> +	}
>> +}
> I wonder if that would be better as "kvfree(memset(...))" as memset() will
> return the address parameter.  If memset is not inline, it avoids the need for
> the compiler to save the parameter.
>
> David

Doing this is micro-optimization. As the keys subsystem is that
performance critical, do we need to do that to save a cycle or two while
making the code a bit harder to read?

Cheers,
Longman