[PATCH] - silence UBSAN complaint in ehci-hcd.

From: Valdis Kletnieks
Date: Thu May 19 2016 - 19:58:51 EST


UBSAN throws a complaint:

[ 2.418579] UBSAN: Undefined behaviour in drivers/usb/host/ehci-hub.c:877:47
[ 2.418582] index -1 is out of range for type 'u32 [1]'

though it's only on the hostpc[] part, not on the port_status[] on the
previous line which has the same exact index calculation. The root cause is
that the first declaration is port_status[0], which uses a GCC extension and
UBSAN is smart enough to realize the programmer is doing something
intentionally odd.

However, the problematic declaration is hostpc[1], which doesn't have
the "I know what I'm doing" semantics of [0]. Change the declaration to match.

Signed-Off-By: Valdis Kletnieks <valdis.kletnieks@xxxxxx>

--- a/include/linux/usb/ehci_def.h 2015-01-06 01:04:24.342436706 -0500
+++ b/include/linux/usb/ehci_def.h 2016-05-19 13:57:20.869304540 -0400
@@ -180,11 +180,11 @@ struct ehci_regs {
* PORTSCx
*/
/* HOSTPC: offset 0x84 */
- u32 hostpc[1]; /* HOSTPC extension */
+ u32 hostpc[0]; /* HOSTPC extension */
#define HOSTPC_PHCD (1<<22) /* Phy clock disable */
#define HOSTPC_PSPD (3<<25) /* Port speed detection */

- u32 reserved5[16];
+ u32 reserved5[17];

/* USBMODE_EX: offset 0xc8 */
u32 usbmode_ex; /* USB Device mode extension */