[PATCH v2] usb: core: Warn if an URB's transfer_buffer is on stack

[Florian Fainelli <f.fainelli@gmail.com>]

We see a large number of fixes to several drivers to remove the usage of
on-stack buffers feeding into USB transfer functions. Make it easier to spot
the offenders by adding a warning in usb_hcd_map_urb_for_dma() checking that
urb->transfer_buffer is not a stack object.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
Changes in v2:

- moved the check from usb_start_wait_urb() to usb_hcd_map_urb_for_dma()

 drivers/usb/core/hcd.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 49550790a3cb..ce9063ce906a 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -26,6 +26,7 @@
 #include <linux/module.h>
 #include <linux/version.h>
 #include <linux/kernel.h>
+#include <linux/sched/task_stack.h>
 #include <linux/slab.h>
 #include <linux/completion.h>
 #include <linux/utsname.h>
@@ -1587,6 +1588,9 @@ int usb_hcd_map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
 			} else if (is_vmalloc_addr(urb->transfer_buffer)) {
 				WARN_ONCE(1, "transfer buffer not dma capable\n");
 				ret = -EAGAIN;
+			} else if (object_is_on_stack(urb->transfer_buffer)) {
+				WARN_ONCE(1, "transfer buffer is on stack\n");
+				ret = -EAGAIN;
 			} else {
 				urb->transfer_dma = dma_map_single(
 						hcd->self.sysdev,
-- 
2.11.0