linux-kernel - [PATCH 44/91] TPM: Zero buffer after copying to userspace

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Date:	Sun, 05 Feb 2012 23:10:33 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Rajiv Andrade <srajiv@...ux.vnet.ibm.com>,
	James Morris <jmorris@...ei.org>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: [PATCH 44/91] TPM: Zero buffer after copying to userspace

2.6.27-longterm review patch.  If anyone has any objections, please let us know.

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

commit 3321c07ae5068568cd61ac9f4ba749006a7185c9 upstream.

Since the buffer might contain security related data it might be a good idea to
zero the buffer after we have copied it to userspace.

This got assigned CVE-2011-1162.

Signed-off-by: Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
Signed-off-by: James Morris <jmorris@...ei.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 drivers/char/tpm/tpm.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

Index: longterm-2.6.27/drivers/char/tpm/tpm.c
===================================================================
--- longterm-2.6.27.orig/drivers/char/tpm/tpm.c	2012-02-05 22:34:40.951915689 +0100
+++ longterm-2.6.27/drivers/char/tpm/tpm.c	2012-02-05 22:34:41.090914667 +0100
@@ -1069,6 +1069,7 @@
 {
 	struct tpm_chip *chip = file->private_data;
 	ssize_t ret_size;
+	int rc;
 
 	del_singleshot_timer_sync(&chip->user_read_timer);
 	flush_scheduled_work();
@@ -1079,8 +1080,11 @@
 			ret_size = size;
 
 		mutex_lock(&chip->buffer_mutex);
-		if (copy_to_user(buf, chip->data_buffer, ret_size))
+		rc = copy_to_user(buf, chip->data_buffer, ret_size);
+		memset(chip->data_buffer, 0, ret_size);
+		if (rc)
 			ret_size = -EFAULT;
+
 		mutex_unlock(&chip->buffer_mutex);
 	}
 


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