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SubjectRe: [PATCH v5 3/8] crypto: AF_ALG: add AEAD support
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Am Montag, 22. Dezember 2014, 22:23:41 schrieb Herbert Xu:

Hi Herbert,

> On Sun, Dec 07, 2014 at 11:22:30PM +0100, Stephan Mueller wrote:
> > +static inline bool aead_sufficient_data(struct aead_ctx *ctx)
> > +{
> > + unsigned as = crypto_aead_authsize(crypto_aead_reqtfm(&ctx-
>aead_req));
> > +
> > + return (ctx->used >= (ctx->aead_assoclen + ctx->enc ? : as ));
>
> Is this supposed to be
>
> return (ctx->used >= (ctx->aead_assoclen + (ctx->enc ?: as)));

Thanks, will be fixed in the next iteration
>
> > +static int aead_recvmsg(struct kiocb *unused, struct socket *sock,
> > + struct msghdr *msg, size_t ignored, int flags)
> > +{
>
> ...
>
> > + err = -ENOMEM;
> > + if (!aead_sufficient_data(ctx))
> > + goto unlock;
>
> You should just block if there is insufficient input.
>
I do not concur here due to the following:

- the check aead_readable() immediately before this check implements the
blocking if we do not have sufficient data *and* more data is to be expected

- this very check for aead_sufficient_data() comes into play if the caller
does not have more data (i.e. ctx->more is zero). In this case, more data is
not to be expected and we cannot wait as this would be a deadlock in user
space.

--
Ciao
Stephan


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