[SRU] [F/G/Unstable/OEM-5.6/OEM-5.10] [PATCH 0/1] Fix reading speed and duplex sysfs on igc device

[Kai-Heng Feng]

BugLink: https://bugs.launchpad.net/bugs/1906851

[Impact]
Reading speed and duplex sysfs on igc device when it's runtime suspended
will make it stops working. Even kernel panic sometimes.

[Fix]
If igc device is runtime suspended, it means link isn't up, so we can
just report speed as -1 and duplex as unknown.

[Test]
$ cat /sys/class/net/*/speed
Then we'll see:
[  123.449883] igc 0000:03:00.0 enp3s0: PCIe link lost, device now detached
[  123.450052] BUG: kernel NULL pointer dereference, address: 0000000000000008

With the fix applied,
$ cat /sys/class/net/*/speed
-1

[Where problems could occur]
Not at all. Reading register when device is runtime suspended is just
wrong. The fix prevents it from happening.

Kai-Heng Feng (1):
  igc: Report speed and duplex as unknown when device is runtime
    suspended

 drivers/net/ethernet/intel/igc/igc_ethtool.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

-- 
2.29.2