linux-kernel - Re: [PATCH RESEND v3] tpm: fix an invalid condition in tpm_common

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Message-ID: <20190325140954.GA13699@linux.intel.com>
Date:   Mon, 25 Mar 2019 16:09:54 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Tadeusz Struk <tadeusz.struk@...el.com>
Cc:     grawity@...il.com, James.Bottomley@...senPartnership.com,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH RESEND v3] tpm: fix an invalid condition in
 tpm_common_poll

On Fri, Mar 22, 2019 at 05:59:17PM +0200, Jarkko Sakkinen wrote:
> On Fri, Mar 22, 2019 at 07:38:58AM -0700, Tadeusz Struk wrote:
> > The poll condition should only check response_length,
> > because reads should only be issued if there is data to read.
> > The response_read flag only prevents double writes.
> > The problem was that the write set the response_read to false,
> > enqued a tpm job, and returned. Then application called poll
> > which checked the response_read flag and returned EPOLLIN.
> > Then the application called read, but got nothing.
> > After all that the async_work kicked in.
> > Added also mutex_lock around the poll check to prevent
> > other possible race conditions.
> > 
> > Cc: stable@...r.kernel.org
> > Fixes: 9488585b21bef0df12 ("tpm: add support for partial reads")
> > Reported-by: Mantas Mikulėnas <grawity@...il.com>
> > Tested-by: Mantas Mikulėnas <grawity@...il.com>
> > Signed-off-by: Tadeusz Struk <tadeusz.struk@...el.com>
> 
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

It is still missing the comment I asked to add. Otherwise, it is good.

/Jarkko