netdev - [PATCH] net: mdio: fix undefined behavior in bit shift for __mdiobus

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Date:   Mon, 31 Oct 2022 14:01:16 +0800
From:   Gaosheng Cui <cuigaosheng1@...wei.com>
To:     <andrew@...n.ch>, <hkallweit1@...il.com>, <linux@...linux.org.uk>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <afleming@...escale.com>,
        <buytenh@...tstofly.org>, <cuigaosheng1@...wei.com>
CC:     <netdev@...r.kernel.org>
Subject: [PATCH] net: mdio: fix undefined behavior in bit shift for __mdiobus_register

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@...wei.com>
---
 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..0cbd9ee87514 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 & (1U << i)) == 0) {
 			struct phy_device *phydev;
 
 			phydev = mdiobus_scan(bus, i);
-- 
2.25.1