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

From: Greg KH
Date: Fri Mar 30 2012 - 17:50:54 EST

3.3-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
@@ -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;

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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