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

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Message-ID: <20190322113401.GL3122@linux.intel.com>
Date:   Fri, 22 Mar 2019 13:34:01 +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 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.
> 

Cc: stable@...r.kernel.org

is missing here.

> 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>

/Jarkko