linux-kernel - [PATCH AUTOSEL 5.4 12/25] media: airspy: respect the DMA coherency rules

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Message-Id: <20220811160826.1541971-12-sashal@kernel.org>
Date:   Thu, 11 Aug 2022 12:08:07 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Oliver Neukum <oneukum@...e.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sasha Levin <sashal@...nel.org>, crope@....fi,
        linux-media@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 12/25] media: airspy: respect the DMA coherency rules

From: Oliver Neukum <oneukum@...e.com>

[ Upstream commit ca9dc8d06ab64543a6a31adac5003349c5671218 ]

If we want to avoid memory corruption
on incoherent architectures, buffers for DMA
must not reside
- on the stack
- embedded within other structures

Allocate them separately.

v2: fix uninitialized return value

Signed-off-by: Oliver Neukum <oneukum@...e.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/usb/airspy/airspy.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/airspy/airspy.c b/drivers/media/usb/airspy/airspy.c
index 751703db06f5..c7499787bffe 100644
--- a/drivers/media/usb/airspy/airspy.c
+++ b/drivers/media/usb/airspy/airspy.c
@@ -123,7 +123,7 @@ struct airspy {
 
 	/* USB control message buffer */
 	#define BUF_SIZE 128
-	u8 buf[BUF_SIZE];
+	u8 *buf;
 
 	/* Current configuration */
 	unsigned int f_adc;
@@ -856,6 +856,7 @@ static void airspy_video_release(struct v4l2_device *v)
 
 	v4l2_ctrl_handler_free(&s->hdl);
 	v4l2_device_unregister(&s->v4l2_dev);
+	kfree(s->buf);
 	kfree(s);
 }
 
@@ -963,7 +964,10 @@ static int airspy_probe(struct usb_interface *intf,
 {
 	struct airspy *s;
 	int ret;
-	u8 u8tmp, buf[BUF_SIZE];
+	u8 u8tmp, *buf;
+
+	buf = NULL;
+	ret = -ENOMEM;
 
 	s = kzalloc(sizeof(struct airspy), GFP_KERNEL);
 	if (s == NULL) {
@@ -971,6 +975,13 @@ static int airspy_probe(struct usb_interface *intf,
 		return -ENOMEM;
 	}
 
+	s->buf = kzalloc(BUF_SIZE, GFP_KERNEL);
+	if (!s->buf)
+		goto err_free_mem;
+	buf = kzalloc(BUF_SIZE, GFP_KERNEL);
+	if (!buf)
+		goto err_free_mem;
+
 	mutex_init(&s->v4l2_lock);
 	mutex_init(&s->vb_queue_lock);
 	spin_lock_init(&s->queued_bufs_lock);
@@ -1068,6 +1079,8 @@ static int airspy_probe(struct usb_interface *intf,
 	v4l2_ctrl_handler_free(&s->hdl);
 	v4l2_device_unregister(&s->v4l2_dev);
 err_free_mem:
+	kfree(buf);
+	kfree(s->buf);
 	kfree(s);
 	return ret;
 }
-- 
2.35.1