linux-kernel - Re: [tpmdd-devel] [PATCH RFC v2 5/5] tpm2: expose resource manager via a device link /dev/tpms<n>

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Message-ID: <1484250369.5807.11.camel@HansenPartnership.com>
Date:   Thu, 12 Jan 2017 11:46:09 -0800
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        tpmdd-devel@...ts.sourceforge.net
Cc:     open list <linux-kernel@...r.kernel.org>,
        linux-security-module@...r.kernel.org
Subject: Re: [tpmdd-devel] [PATCH RFC v2 5/5] tpm2: expose resource manager
 via    a device link /dev/tpms<n>

On Thu, 2017-01-12 at 19:46 +0200, Jarkko Sakkinen wrote:
> From: James Bottomley <James.Bottomley@...senPartnership.com>
> 
> Currently the Resource Manager (RM) is not exposed to userspace. 
>  Make
> this exposure via a separate device, which can now be opened multiple
> times because each read/write transaction goes separately via the RM.
> 
> Concurrency is protected by the chip->tpm_mutex for each read/write
> transaction separately.  The TPM is cleared of all transient objects
> by the time the mutex is dropped, so there should be no interference
> between the kernel and userspace.

There's a bug in this code that will crash on first command.  This is
the incremental fix.  It must have got lost when I did the split.

James

---

diff --git a/drivers/char/tpm/tpms-dev.c b/drivers/char/tpm/tpms-dev.c
index f4cb7a3..3eb5955 100644
--- a/drivers/char/tpm/tpms-dev.c
+++ b/drivers/char/tpm/tpms-dev.c
@@ -20,6 +20,11 @@ static int tpms_open(struct inode *inode, struct file *file)
 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 	if (priv == NULL)
 		return -ENOMEM;
+	priv->space.context_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (priv->space.context_buf == NULL) {
+		kfree(priv);
+		return -ENOMEM;
+	}
 
 	tpm_common_open(file, chip, &priv->priv);