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Subject[036/107] TPM: Zero buffer after copying to userspace
2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------
From: Peter Huewe <huewe.external.infineon@googlemail.com>

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>

---
drivers/char/tpm/tpm.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -1044,6 +1044,7 @@ ssize_t tpm_read(struct file *file, char
{
struct tpm_chip *chip = file->private_data;
ssize_t ret_size;
+ int rc;

del_singleshot_timer_sync(&chip->user_read_timer);
flush_scheduled_work();
@@ -1054,8 +1055,11 @@ ssize_t tpm_read(struct file *file, char
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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