TPM: Zero buffer after copying to userspace

BugLink: http://bugs.launchpad.net/bugs/868628

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@linux.vnet.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index 92676292bea..b85ee76e4b4 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -1055,6 +1055,7 @@ ssize_t tpm_read(struct file *file, char __user *buf,
 {
         struct tpm_chip *chip = file->private_data;
         ssize_t ret_size;
+        int rc;
 
         del_singleshot_timer_sync(&chip->user_read_timer);
         flush_work_sync(&chip->work);
@@ -1065,8 +1066,11 @@ ssize_t tpm_read(struct file *file, char __user *buf,
                         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);
         }