[PATCH v2] net: mdio: fix undefined behavior in bit shift for __mdiobus_register

[Gaosheng Cui <cuigaosheng1@huawei.com>]

Shifting signed 32-bit value by 31 bits is undefined, so changing
significant bit to unsigned. The UBSAN warning calltrace like below:

UBSAN: shift-out-of-bounds in drivers/net/phy/mdio_bus.c:586:27
left shift of 1 by 31 places cannot be represented in type 'int'
Call Trace:
 <TASK>
 dump_stack_lvl+0x7d/0xa5
 dump_stack+0x15/0x1b
 ubsan_epilogue+0xe/0x4e
 __ubsan_handle_shift_out_of_bounds+0x1e7/0x20c
 __mdiobus_register+0x49d/0x4e0
 fixed_mdio_bus_init+0xd8/0x12d
 do_one_initcall+0x76/0x430
 kernel_init_freeable+0x3b3/0x422
 kernel_init+0x24/0x1e0
 ret_from_fork+0x1f/0x30
 </TASK>

Fixes: 4fd5f812c23c ("phylib: allow incremental scanning of an mii bus")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
---
v2:
- Use the BIT() macro, thanks!
 drivers/net/phy/mdio_bus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index f82090bdf7ab..1cd604cd1fa1 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -583,7 +583,7 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 	}
 
 	for (i = 0; i < PHY_MAX_ADDR; i++) {
-		if ((bus->phy_mask & (1 << i)) == 0) {
+		if ((bus->phy_mask & BIT(i)) == 0) {
 			struct phy_device *phydev;
 
 			phydev = mdiobus_scan(bus, i);
-- 
2.25.1