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

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Message-ID: <20190322051802.GA17257@kroah.com>
Date:   Fri, 22 Mar 2019 06:18:02 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Tadeusz Struk <tadeusz.struk@...el.com>
Cc:     jarkko.sakkinen@...ux.intel.com, grawity@...il.com,
        James.Bottomley@...senpartnership.com,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v3] tpm: fix an invalid condition in tpm_common_poll

On Thu, Mar 21, 2019 at 04:02:12PM -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.
> 
> 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>
> ---
>  drivers/char/tpm/tpm-dev-common.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>