linux-kernel - [PATCH 1/3] TPM: Zero buffer whole after copying to userspace

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Date:	Tue,  6 Dec 2011 11:29:20 -0700
From:	Tim Gardner <tim.gardner@...onical.com>
To:	linux-kernel@...r.kernel.org
Cc:	Seth Forshee <seth.forshee@...onical.com>,
	Tim Gardner <tim.gardner@...onical.com>,
	Debora Velarde <debora@...ux.vnet.ibm.com>,
	Rajiv Andrade <srajiv@...ux.vnet.ibm.com>,
	Marcel Selhorst <m.selhorst@...rix.com>,
	tpmdd-devel@...ts.sourceforge.net, stable@...r.kernel.org
Subject: [PATCH 1/3] TPM: Zero buffer whole after copying to userspace

Commit 3321c07ae5068568cd61ac9f4ba749006a7185c9 correctly clears the TPM
buffer if the user specified read length is >= the TPM buffer length. However,
if the user specified read length is < the TPM buffer length, then part of the
TPM buffer is left uncleared.

Reported-by: Seth Forshee <seth.forshee@...onical.com>
Cc: Debora Velarde <debora@...ux.vnet.ibm.com>
Cc: Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
Cc: Marcel Selhorst <m.selhorst@...rix.com>
Cc: tpmdd-devel@...ts.sourceforge.net
Cc: stable@...r.kernel.org
Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
---
 drivers/char/tpm/tpm.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index 361a1df..b366b34 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -1115,12 +1115,13 @@ ssize_t tpm_read(struct file *file, char __user *buf,
 	ret_size = atomic_read(&chip->data_pending);
 	atomic_set(&chip->data_pending, 0);
 	if (ret_size > 0) {	/* relay data */
+		ssize_t orig_ret_size = ret_size;
 		if (size < ret_size)
 			ret_size = size;
 
 		mutex_lock(&chip->buffer_mutex);
 		rc = copy_to_user(buf, chip->data_buffer, ret_size);
-		memset(chip->data_buffer, 0, ret_size);
+		memset(chip->data_buffer, 0, orig_ret_size);
 		if (rc)
 			ret_size = -EFAULT;
 
-- 
1.7.0.4

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