Patch "net: mdio: fix undefined behavior in bit shift for __mdiobus_register" has been added to the 4.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: mdio: fix undefined behavior in bit shift for __mdiobus_register

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-mdio-fix-undefined-behavior-in-bit-shift-for-__m.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 15797dfcf10c5d0f860e6068d04995bbc974a97d
Author: Gaosheng Cui <cuigaosheng1@xxxxxxxxxx>
Date:   Mon Oct 31 21:26:45 2022 +0800

    net: mdio: fix undefined behavior in bit shift for __mdiobus_register
    
    [ 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@xxxxxxxxxx>
    Reviewed-by: Andrew Lunn <andrew@xxxxxxx>
    Link: https://lore.kernel.org/r/20221031132645.168421-1-cuigaosheng1@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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);