linux-kernel - [PATCH 3.2 31/59] [media] ttusb2: Don't use stack variables for DMA

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Date:   Fri, 18 Aug 2017 14:13:13 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Josh Boyer" <jwboyer@...hat.com>,
        "Mauro Carvalho Chehab" <mchehab@...hat.com>
Subject: [PATCH 3.2 31/59] [media] ttusb2: Don't use stack variables for DMA

3.2.92-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Josh Boyer <jwboyer@...hat.com>

commit ff17999184ed13829bc14c3be412d980173dff40 upstream.

The ttusb2_msg function uses on-stack variables to submit commands to
dvb_usb_generic.  This eventually gets to the DMA api layer and will throw a
traceback if the debugging options are set.

This allocates the temporary buffer variables with kzalloc instead.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=734506

Signed-off-by: Josh Boyer <jwboyer@...hat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/media/dvb/dvb-usb/ttusb2.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

--- a/drivers/media/dvb/dvb-usb/ttusb2.c
+++ b/drivers/media/dvb/dvb-usb/ttusb2.c
@@ -75,10 +75,18 @@ static int ttusb2_msg(struct dvb_usb_dev
 		u8 *wbuf, int wlen, u8 *rbuf, int rlen)
 {
 	struct ttusb2_state *st = d->priv;
-	u8 s[wlen+4],r[64] = { 0 };
+	u8 *s, *r = NULL;
 	int ret = 0;
 
-	memset(s,0,wlen+4);
+	s = kzalloc(wlen+4, GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+
+	r = kzalloc(64, GFP_KERNEL);
+	if (!r) {
+		kfree(s);
+		return -ENOMEM;
+	}
 
 	s[0] = 0xaa;
 	s[1] = ++st->id;
@@ -94,12 +102,17 @@ static int ttusb2_msg(struct dvb_usb_dev
 		r[2] != cmd ||
 		(rlen > 0 && r[3] != rlen)) {
 		warn("there might have been an error during control message transfer. (rlen = %d, was %d)",rlen,r[3]);
+		kfree(s);
+		kfree(r);
 		return -EIO;
 	}
 
 	if (rlen > 0)
 		memcpy(rbuf, &r[4], rlen);
 
+	kfree(s);
+	kfree(r);
+
 	return 0;
 }