[PATCH 4.14 40/57] USB: usblp: fix DMA to stack

Greg Kroah-Hartman
2021-01-11T14:00:12Z

From: Johan Hovold <johan@kernel.org>

commit 020a1f453449294926ca548d8d5ca970926e8dfd upstream.

Stack-allocated buffers cannot be used for DMA (on all architectures).

Replace the HP-channel macro with a helper function that allocates a
dedicated transfer buffer so that it can continue to be used with
arguments from the stack.

Note that the buffer is cleared on allocation as usblp_ctrl_msg()
returns success also on short transfers (the buffer is only used for
debugging).

Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210104145302.2087-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/class/usblp.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)

--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -289,8 +289,25 @@ static int usblp_ctrl_msg(struct usblp *
#define usblp_reset(usblp)\
usblp_ctrl_msg(usblp, USBLP_REQ_RESET, USB_TYPE_CLASS, USB_DIR_OUT, USB_RECIP_OTHER, 0, NULL, 0)

-#define usblp_hp_channel_change_request(usblp, channel, buffer) \
- usblp_ctrl_msg(usblp, USBLP_REQ_HP_CHANNEL_CHANGE_REQUEST, USB_TYPE_VENDOR, USB_DIR_IN, USB_RECIP_INTERFACE, channel, buffer, 1)
+static int usblp_hp_channel_change_request(struct usblp *usblp, int channel, u8 *new_channel)
+{
+ u8 *buf;
+ int ret;
+
+ buf = kzalloc(1, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ ret = usblp_ctrl_msg(usblp, USBLP_REQ_HP_CHANNEL_CHANGE_REQUEST,
+ USB_TYPE_VENDOR, USB_DIR_IN, USB_RECIP_INTERFACE,
+ channel, buf, 1);
+ if (ret == 0)
+ *new_channel = buf[0];
+
+ kfree(buf);
+
+ return ret;
+}

/*
* See the description for usblp_select_alts() below for the usage