From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Tadeusz Struk <tadeusz.struk@intel.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: "Mantas Mikulėnas" <grawity@gmail.com>, linux-integrity@vger.kernel.org
Subject: Re: Kernel 5.0 regression in /dev/tpm0 access
Date: Tue, 12 Mar 2019 15:50:49 -0700 [thread overview]
Message-ID: <1552431049.14432.42.camel@HansenPartnership.com> (raw)
In-Reply-To: <14297706-74ef-f178-3b65-e63289919117@intel.com>
On Tue, 2019-03-12 at 15:42 -0700, Tadeusz Struk wrote:
> @@ -202,13 +196,15 @@ __poll_t tpm_common_poll(struct file *file,
> poll_table *wait)
> struct file_priv *priv = file->private_data;
> __poll_t mask = 0;
>
> + mutex_lock(&priv->buffer_mutex);
> poll_wait(file, &priv->async_wait, wait);
>
> - if (!priv->response_read || priv->response_length)
> + if (priv->response_length)
> mask = EPOLLIN | EPOLLRDNORM;
> else
> mask = EPOLLOUT | EPOLLWRNORM;
>
> + mutex_unlock(&priv->buffer_mutex);
Isn't this setting us up for a deadlock? If the work queued by write
hasn't run by the time you call poll, you take the buffer mutex and
sleep. Now if the work runs, it blocks acquiring the mutex in
tpm_async_work and never calls wakeup on async_wait.
James
next prev parent reply other threads:[~2019-03-12 22:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-09 20:48 Kernel 5.0 regression in /dev/tpm0 access Mantas Mikulėnas
2019-03-09 22:01 ` James Bottomley
2019-03-09 22:44 ` James Bottomley
2019-03-11 13:09 ` Jarkko Sakkinen
2019-03-12 22:42 ` Tadeusz Struk
2019-03-12 22:50 ` James Bottomley [this message]
2019-03-13 14:00 ` Jarkko Sakkinen
2019-03-13 13:59 ` Jarkko Sakkinen
2019-03-17 13:22 ` Jarkko Sakkinen
2019-03-18 15:50 ` Tadeusz Struk
2019-03-20 9:58 ` Jarkko Sakkinen
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