ethtool: check device is present when getting link settings

Vulnerability Description

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.

References

• https://git.kernel.org/stable/c/ec7b4f7f644018ac293cb1b02528a40a32917e62
• https://git.kernel.org/stable/c/842a40c7273ba1c1cb30dda50405b328de1d860e
• https://git.kernel.org/stable/c/7a8d98b6d6484d3ad358510366022da080c37cbc
• https://git.kernel.org/stable/c/9bba5955eed160102114d4cc00c3d399be9bdae4
• https://git.kernel.org/stable/c/94ab317024ba373d37340893d1c0358638935fbb
• https://git.kernel.org/stable/c/1d6d9b5b1b95bfeccb84386a51b7e6c510ec13b2
• https://git.kernel.org/stable/c/a699781c79ecf6cfe67fb00a0331b4088c7c8466