[PATCH v2] hid: hid-led: fix issue with transfer buffer not being dma capable

[Heiner Kallweit <hkallweit1@gmail.com>]

The hid-led driver works fine under 4.8.0, however with the next
kernel from today I get this:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 2578 at drivers/usb/core/hcd.c:1584 usb_hcd_map_urb_for_dma+0x373/0x550 [usbcore]
transfer buffer not dma capable
Modules linked in: hid_led(+) usbhid vfat fat ir_sony_decoder iwlmvm led_class mac80211 snd_hda_codec_realtek snd_hda_codec_generic x86_pkg_temp_thermal iwlwifi crc32c_intel snd_hda_codec_hdmi i2c_i801 i2c_smbus snd_hda_intel cfg80211 snd_hda_codec snd_hda_core snd_pcm r8169 snd_timer mei_me mii snd mei ir_lirc_codec lirc_dev nuvoton_cir rc_core btusb btintel bluetooth rfkill usb_storage efivarfs ipv6 ehci_pci ehci_hcd xhci_pci xhci_hcd usbcore usb_common ext4 jbd2 mbcache ahci libahci libata
CPU: 0 PID: 2578 Comm: systemd-udevd Not tainted 4.8.0-rc8-next-20161003 #1
Hardware name: ZOTAC ZBOX-CI321NANO/ZBOX-CI321NANO, BIOS B246P105 06/01/2015
 ffffc90003dbb7e0 ffffffff81280425 ffffc90003dbb830 0000000000000000
 ffffc90003dbb820 ffffffff8105b086 0000063003dbb800 ffff88006f374480
 0000000000000000 0000000000000000 0000000000000001 ffff880079544000
Call Trace:
 [<ffffffff81280425>] dump_stack+0x68/0x93
 [<ffffffff8105b086>] __warn+0xc6/0xe0
 [<ffffffff8105b0ea>] warn_slowpath_fmt+0x4a/0x50
 [<ffffffffa0143a43>] usb_hcd_map_urb_for_dma+0x373/0x550 [usbcore]
 [<ffffffffa01441b6>] usb_hcd_submit_urb+0x316/0x9c0 [usbcore]
 [<ffffffff810bce80>] ? rcu_read_lock_sched_held+0x40/0x80
 [<ffffffff810e0043>] ? module_assert_mutex_or_preempt+0x13/0x50
 [<ffffffff810e0c07>] ? __module_address+0x27/0xf0
 [<ffffffffa01456e4>] usb_submit_urb+0x2c4/0x520 [usbcore]
 [<ffffffffa0145fea>] usb_start_wait_urb+0x5a/0xe0 [usbcore]
 [<ffffffffa014612c>] usb_control_msg+0xbc/0xf0 [usbcore]
 [<ffffffff810e0c07>] ? __module_address+0x27/0xf0
 [<ffffffffa079a724>] usbhid_raw_request+0xa4/0x180 [usbhid]
 [<ffffffffa07a93b1>] hidled_recv+0x71/0xe0 [hid_led]
 [<ffffffffa07a947d>] thingm_init+0x2d/0x50 [hid_led]
 [<ffffffffa07a969b>] hidled_probe+0xcb/0x24a [hid_led]
 [<ffffffff814d96f2>] hid_device_probe+0xd2/0x150
 [<ffffffff8146023d>] driver_probe_device+0x1fd/0x2c0
 [<ffffffff8146039a>] __driver_attach+0x9a/0xa0
 [<ffffffff81460300>] ? driver_probe_device+0x2c0/0x2c0
 [<ffffffff8145e25d>] bus_for_each_dev+0x5d/0x90
 [<ffffffff8145fa79>] driver_attach+0x19/0x20
 [<ffffffff8145f5ff>] bus_add_driver+0x11f/0x220
 [<ffffffffa07ac000>] ? 0xffffffffa07ac000
 [<ffffffff8146086b>] driver_register+0x5b/0xd0
 [<ffffffffa07ac000>] ? 0xffffffffa07ac000
 [<ffffffff814d83d1>] __hid_register_driver+0x61/0xa0
 [<ffffffffa07ac01e>] hidled_driver_init+0x1e/0x20 [hid_led]
 [<ffffffff81000408>] do_one_initcall+0x38/0x150
 [<ffffffff810bce80>] ? rcu_read_lock_sched_held+0x40/0x80
 [<ffffffff81194ca0>] ? kmem_cache_alloc_trace+0x1d0/0x230
 [<ffffffff811342f9>] do_init_module+0x5a/0x1cb
 [<ffffffff810e3862>] load_module+0x1e42/0x2530
 [<ffffffff810e0990>] ? __symbol_put+0x50/0x50
 [<ffffffff810dfc50>] ? show_coresize+0x30/0x30
 [<ffffffff811ad650>] ? kernel_read_file+0x100/0x190
 [<ffffffff811ad794>] ? kernel_read_file_from_fd+0x44/0x70
 [<ffffffff810e415a>] SYSC_finit_module+0xba/0xc0
 [<ffffffff810e4179>] SyS_finit_module+0x9/0x10
 [<ffffffff815e082a>] entry_SYSCALL_64_fastpath+0x18/0xad
---[ end trace c9e6ea27003ecf9e ]---

Fix this by using a kmalloc'ed buffer when calling hid_hw_raw_request.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
v2:
- Based on a comment from Alan Stern allocate the buffer to be provided to
  hid_hw_raw_request separately (and not as part of struct hidled_device).
  Alternative would have been to allocate the buffer dynamically in each
  function calling hidled_send/_recv. However this would mean more overhead
  IMHO, and we'd need an error path in callers to free the buffer in case
  of an error.
  In addition we have better control that a proper buffer is used in case
  the driver is extended by somebody for supporting another LED device.
---
 drivers/hid/hid-led.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/hid-led.c b/drivers/hid/hid-led.c
index d8d55f3..555c88e 100644
--- a/drivers/hid/hid-led.c
+++ b/drivers/hid/hid-led.c
@@ -100,6 +100,7 @@ struct hidled_device {
 	const struct hidled_config *config;
 	struct hid_device       *hdev;
 	struct hidled_rgb	*rgb;
+	u8			*buf;
 	struct mutex		lock;
 };
 
@@ -118,13 +119,19 @@ static int hidled_send(struct hidled_device *ldev, __u8 *buf)
 
 	mutex_lock(&ldev->lock);
 
+	/*
+	 * buffer provided to hid_hw_raw_request must not be on the stack
+	 * and must not be part of a data structure
+	 */
+	memcpy(ldev->buf, buf, ldev->config->report_size);
+
 	if (ldev->config->report_type == RAW_REQUEST)
-		ret = hid_hw_raw_request(ldev->hdev, buf[0], buf,
+		ret = hid_hw_raw_request(ldev->hdev, buf[0], ldev->buf,
 					 ldev->config->report_size,
 					 HID_FEATURE_REPORT,
 					 HID_REQ_SET_REPORT);
 	else if (ldev->config->report_type == OUTPUT_REPORT)
-		ret = hid_hw_output_report(ldev->hdev, buf,
+		ret = hid_hw_output_report(ldev->hdev, ldev->buf,
 					   ldev->config->report_size);
 	else
 		ret = -EINVAL;
@@ -147,17 +154,21 @@ static int hidled_recv(struct hidled_device *ldev, __u8 *buf)
 
 	mutex_lock(&ldev->lock);
 
-	ret = hid_hw_raw_request(ldev->hdev, buf[0], buf,
+	memcpy(ldev->buf, buf, ldev->config->report_size);
+
+	ret = hid_hw_raw_request(ldev->hdev, buf[0], ldev->buf,
 				 ldev->config->report_size,
 				 HID_FEATURE_REPORT,
 				 HID_REQ_SET_REPORT);
 	if (ret < 0)
 		goto err;
 
-	ret = hid_hw_raw_request(ldev->hdev, buf[0], buf,
+	ret = hid_hw_raw_request(ldev->hdev, buf[0], ldev->buf,
 				 ldev->config->report_size,
 				 HID_FEATURE_REPORT,
 				 HID_REQ_GET_REPORT);
+
+	memcpy(buf, ldev->buf, ldev->config->report_size);
 err:
 	mutex_unlock(&ldev->lock);
 
@@ -447,6 +458,10 @@ static int hidled_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	if (!ldev)
 		return -ENOMEM;
 
+	ldev->buf = devm_kmalloc(&hdev->dev, MAX_REPORT_SIZE, GFP_KERNEL);
+	if (!ldev->buf)
+		return -ENOMEM;
+
 	ret = hid_parse(hdev);
 	if (ret)
 		return ret;
-- 
2.10.0