USB: usblp: fix DMA to stack

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>

diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 67cbd42421bee7e5776659a5f7ebfb077564a457..134dc2005ce97de81ee1787510d4772395da8ef4 100644 (file)
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -274,8 +274,25 @@ static int usblp_ctrl_msg(struct usblp *usblp, int request, int type, int dir, i
 #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