linux-kernel - Re: Issue with iwd + Linux 5.8.3 + WPA Enterprise

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Message-ID: <20200826141907.GA5111@gondor.apana.org.au>
Date:   Thu, 27 Aug 2020 00:19:08 +1000
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Denis Kenzior <denkenz@...il.com>
Cc:     Andrew Zaborowski <andrew.zaborowski@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        Caleb Jorden <caljorden@...mail.com>,
        Sasha Levin <sashal@...nel.org>, iwd@...ts.01.org,
        "# 3.4.x" <stable@...r.kernel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>
Subject: Re: Issue with iwd + Linux 5.8.3 + WPA Enterprise

On Wed, Aug 26, 2020 at 08:57:17AM -0500, Denis Kenzior wrote:
> 
> I'm just waking up now, so I might seem dense, but for my education, can you
> tell me why we need to set MSG_MORE when we issue just a single sendmsg
> followed immediately by recv/recvmsg? ell/iwd operates on small buffers, so
> we don't really feed the kernel data in multiple send operations.  You can
> see this in the ell git tree link referenced in Andrew's reply.

You obviously don't need MSG_MORE if you're doing a single sendmsg.

The problematic code is in l_cipher_set_iv.  It does a sendmsg(2)
that expects to be followed by more sendmsg(2) calls before a
recvmsg(2).  That's the one that needs a MSG_MORE.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt