[ 056/149] TPM: Zero buffer whole after copying to userspace

[Greg KH]

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

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

From: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Cc: Debora Velarde <debora@xxxxxxxxxxxxxxxxxx>
Cc: Rajiv Andrade <srajiv@xxxxxxxxxxxxxxxxxx>
Cc: Marcel Selhorst <m.selhorst@xxxxxxxxxx>
Cc: tpmdd-devel@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>
Signed-off-by: Rajiv Andrade <srajiv@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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
@@ -1115,12 +1115,13 @@ 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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