CVE-2024-46679

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

ethtool: check device is present when getting link settings

A sysfs reader can race with a device reset or removal, attempting to

read device state when the device is not actually present. eg:

[exception RIP: qed_get_current_link+17]

#8 [ffffb9e4f2907c48] qede_get_link_ksettings at ffffffffc07a994a [qede]

#9 [ffffb9e4f2907cd8] __rh_call_get_link_ksettings at ffffffff992b01a3

#10 [ffffb9e4f2907d38] __ethtool_get_link_ksettings at ffffffff992b04e4

#11 [ffffb9e4f2907d90] duplex_show at ffffffff99260300

#12 [ffffb9e4f2907e38] dev_attr_show at ffffffff9905a01c

#13 [ffffb9e4f2907e50] sysfs_kf_seq_show at ffffffff98e0145b

#14 [ffffb9e4f2907e68] seq_read at ffffffff98d902e3

#15 [ffffb9e4f2907ec8] vfs_read at ffffffff98d657d1

#16 [ffffb9e4f2907f00] ksys_read at ffffffff98d65c3f

#17 [ffffb9e4f2907f38] do_syscall_64 at ffffffff98a052fb

crash> struct net_device.state ffff9a9d21336000

state = 5,

state 5 is __LINK_STATE_START (0b1) and __LINK_STATE_NOCARRIER (0b100).

The device is not present, note lack of __LINK_STATE_PRESENT (0b10).

This is the same sort of panic as observed in commit 4224cfd7fb65

("net-sysfs: add check for netdevice being present to speed_show").

There are many other callers of __ethtool_get_link_ksettings() which

don't have a device presence check.

Move this check into ethtool to protect all callers.