linux-ext4 - Re: [PATCH 5/6] fscrypt: cache the HMAC transform for each master key

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Date:   Wed, 19 Jul 2017 10:37:44 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     Michael Halcrow <mhalcrow@...gle.com>
Cc:     linux-fscrypt@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-mtd@...ts.infradead.org, linux-crypto@...r.kernel.org,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Alex Cope <alexcope@...gle.com>,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH 5/6] fscrypt: cache the HMAC transform for each master key

On Mon, Jul 17, 2017 at 10:45:51AM -0700, Michael Halcrow wrote:
> > +/*
> > + * Get the fscrypt_master_key identified by the specified v2+ encryption
> > + * context, or create it if not found.
> > + *
> > + * Returns the fscrypt_master_key with a reference taken, or an ERR_PTR().
> > + */
> > +static struct fscrypt_master_key *
> > +find_or_create_master_key(const struct inode *inode,
> > +			  const struct fscrypt_context *ctx,
> > +			  unsigned int min_keysize)
> > +{
> > +	struct fscrypt_master_key *master_key;
> > +
> > +	if (WARN_ON(ctx->version < FSCRYPT_CONTEXT_V2))
> > +		return ERR_PTR(-EINVAL);
> 
> Isn't this a programming error?  If so, consider either BUG_ON() or
> omit the check.
> 

Yes, but BUG_ON() is discouraged in cases where there is a straightforward way
to recover from the error.  checkpatch actually warns about using it these days.

Eric