[PATCH 4.9 043/120] wusbcore: Fix one more crypto-on-the-stack bug

[Greg Kroah-Hartman]

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

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

From: Andy Lutomirski <luto@xxxxxxxxxx>

commit 620f1a632ebcc9811c2f8009ba52297c7006f805 upstream.

The driver put a constant buffer of all zeros on the stack and
pointed a scatterlist entry at it.  This doesn't work with virtual
stacks.  Use ZERO_PAGE instead.

Reported-by: Eric Biggers <ebiggers3@xxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/wusbcore/crypto.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/usb/wusbcore/crypto.c
+++ b/drivers/usb/wusbcore/crypto.c
@@ -216,7 +216,6 @@ static int wusb_ccm_mac(struct crypto_sk
 	struct scatterlist sg[4], sg_dst;
 	void *dst_buf;
 	size_t dst_size;
-	const u8 bzero[16] = { 0 };
 	u8 iv[crypto_skcipher_ivsize(tfm_cbc)];
 	size_t zero_padding;
 
@@ -261,7 +260,7 @@ static int wusb_ccm_mac(struct crypto_sk
 	sg_set_buf(&sg[1], &scratch->b1, sizeof(scratch->b1));
 	sg_set_buf(&sg[2], b, blen);
 	/* 0 if well behaved :) */
-	sg_set_buf(&sg[3], bzero, zero_padding);
+	sg_set_page(&sg[3], ZERO_PAGE(0), zero_padding, 0);
 	sg_init_one(&sg_dst, dst_buf, dst_size);
 
 	skcipher_request_set_tfm(req, tfm_cbc);