Patch "mcs7780: Fix initialization when CONFIG_VMAP_STACK is enabled" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

mcs7780: Fix initialization when CONFIG_VMAP_STACK is enabled

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mcs7780-fix-initialization-when-config_vmap_stack-is-enabled.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Thomas Jarosch <[email protected]>
Date: Sat, 22 Jul 2017 17:14:34 +0200
Subject: mcs7780: Fix initialization when CONFIG_VMAP_STACK is enabled

From: Thomas Jarosch <[email protected]>

[ Upstream commit 9476d393667968b4a02afbe9d35a3558482b943e ]

DMA transfers are not allowed to buffers that are on the stack. Therefore allocate a buffer to store the result of usb_control_message().

Fixes these bugreports:
https://bugzilla.kernel.org/show_bug.cgi?id=195217

https://bugzilla.redhat.com/show_bug.cgi?id=1421387
https://bugzilla.redhat.com/show_bug.cgi?id=1427398

Shortened kernel backtrace from 4.11.9-200.fc25.x86_64:
kernel: ------------[ cut here ]------------
kernel: WARNING: CPU: 3 PID: 2957 at drivers/usb/core/hcd.c:1587
kernel: transfer buffer not dma capable
kernel: Call Trace:
kernel: dump_stack+0x63/0x86
kernel: __warn+0xcb/0xf0
kernel: warn_slowpath_fmt+0x5a/0x80
kernel: usb_hcd_map_urb_for_dma+0x37f/0x570
kernel: ? try_to_del_timer_sync+0x53/0x80
kernel: usb_hcd_submit_urb+0x34e/0xb90
kernel: ? schedule_timeout+0x17e/0x300
kernel: ? del_timer_sync+0x50/0x50
kernel: ? __slab_free+0xa9/0x300
kernel: usb_submit_urb+0x2f4/0x560
kernel: ? urb_destroy+0x24/0x30
kernel: usb_start_wait_urb+0x6e/0x170
kernel: usb_control_msg+0xdc/0x120
kernel: mcs_get_reg+0x36/0x40 [mcs7780]
kernel: mcs_net_open+0xb5/0x5c0 [mcs7780]
...

Regression goes back to 4.9, so it's a good candidate for -stable. Though it's the decision of the maintainer.

Thanks to Dan Williams for adding the "transfer buffer not dma capable" warning in the first place. It instantly pointed me in the right direction.

Patch has been tested with transferring data from a Polar watch.

---
 drivers/net/irda/mcs7780.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

@@ -141,9 +141,19 @@ static int mcs_set_reg(struct mcs_cb *mc
 static int mcs_get_reg(struct mcs_cb *mcs, __u16 reg, __u16 * val)
 {
 	struct usb_device *dev = mcs->usbdev;
-	int ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), MCS_RDREQ,
-				  MCS_RD_RTYPE, 0, reg, val, 2,
-				  msecs_to_jiffies(MCS_CTRL_TIMEOUT));
+	void *dmabuf;
+	int ret;
+
+	dmabuf = kmalloc(sizeof(__u16), GFP_KERNEL);
+	if (!dmabuf)
+		return -ENOMEM;
+
+	ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), MCS_RDREQ,
+			      MCS_RD_RTYPE, 0, reg, dmabuf, 2,
+			      msecs_to_jiffies(MCS_CTRL_TIMEOUT));
+
+	memcpy(val, dmabuf, sizeof(__u16));
+	kfree(dmabuf);
 
 	return ret;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/mcs7780-fix-initialization-when-config_vmap_stack-is-enabled.patch