linux-kernel - [ 063/175] TPM: Zero buffer whole after copying to userspace

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Message-Id: <20120330194836.387542945@linuxfoundation.org>
Date:	Fri, 30 Mar 2012 12:49:28 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Seth Forshee <seth.forshee@...onical.com>,
	Debora Velarde <debora@...ux.vnet.ibm.com>,
	Rajiv Andrade <srajiv@...ux.vnet.ibm.com>,
	Marcel Selhorst <m.selhorst@...rix.com>,
	Tim Gardner <tim.gardner@...onical.com>
Subject: [ 063/175] TPM: Zero buffer whole after copying to userspace

3.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tim Gardner <tim.gardner@...onical.com>

commit 3ab1aff89477dafb1aaeafe8c8669114a02b7226 upstream.

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
Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
Signed-off-by: Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/char/tpm/tpm.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -1221,12 +1221,13 @@ ssize_t tpm_read(struct file *file, char
 	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;
 


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