AZL-64604

In the Linux kernel, the following vulnerability has been resolved:

net: phy: clear phydev->devlink when the link is deleted

There is a potential crash issue when disabling and re-enabling the network port. When disabling the network port, phydetach() calls devicelinkdel() to remove the device link, but it does not clear phydev->devlink, so phydev->devlink is not a NULL pointer. Then the network port is re-enabled, but if phyattachdirect() fails before calling devicelinkadd(), the code jumps to the "error" label and calls phydetach(). Since phydev->devlink retains the old value from the previous attach/detach cycle, devicelinkdel() uses the old value, which accesses a NULL pointer and causes a crash. The simplified crash log is as follows.

[ 24.702421] Call trace: [ 24.704856] devicelinkputkref+0x20/0x120 [ 24.709124] devicelinkdel+0x30/0x48 [ 24.712864] phydetach+0x24/0x168 [ 24.716261] phyattachdirect+0x168/0x3a4 [ 24.720352] phylinkfwnodephyconnect+0xc8/0x14c [ 24.725140] phylinkofphyconnect+0x1c/0x34

Therefore, phydev->devlink needs to be cleared when the device link is deleted.