[PATCH 4.9 16/30] net: mdio: fix undefined behavior in bit shift for __mdiobus_register

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Gaosheng Cui <cuigaosheng1@huawei.com>

[ Upstream commit 40e4eb324c59e11fcb927aa46742d28aba6ecb8a ]

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>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20221031132645.168421-1-cuigaosheng1@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 0fa6e2da4b5a..2aecc5ee9133 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -335,7 +335,7 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 		bus->reset(bus);
 
 	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);
-- 
2.35.1