Fw: [Bug 215950] New: bonding: kernel oops due to possible race with wifi adapters

Fw: [Bug 215950] New: bonding: kernel oops due to possible race with wifi adapters

[Stephen Hemminger]

Begin forwarded message:

Date: Sat, 07 May 2022 06:24:29 +0000
From: bugzilla-daemon@kernel.org
To: stephen@networkplumber.org
Subject: [Bug 215950] New: bonding: kernel oops due to possible race with wifi adapters


https://bugzilla.kernel.org/show_bug.cgi?id=215950

            Bug ID: 215950
           Summary: bonding: kernel oops due to possible race with wifi
                    adapters
           Product: Networking
           Version: 2.5
    Kernel Version: 5.17.5
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Other
          Assignee: stephen@networkplumber.org
          Reporter: smopucilowski@gmail.com
        Regression: No

Created attachment 300899
  --> https://bugzilla.kernel.org/attachment.cgi?id=300899&action=edit  
kernel oops syslog entry

Trying to create a resilient bond with a wired and wireless interface
(https://wiki.archlinux.org/title/systemd-networkd#Bonding_a_wired_and_wireless_interface),
in which the wired interface (ethernet dongle) is spent majority unplugged.
systemd-networkd and iwd are used to manage the interfaces and wireless
connection.

Downstream bug report: https://github.com/systemd/systemd/issues/23255

Kernel oops can be triggered reliably with the systemd-networkd configuration
in the above downstream bug report. On a debug kernel, where kernel timings are
a bit slower, if oops wasn't triggered during boot when systemd-network handles
connections, then restarting iwd and systemd-networkd almost always triggers
it.

The oops appears to be a null deference in bond_slave_state:
include/net/bonding.h:242 return slave->backup;
which suggests a race condition whereby slave interfaces are brought up or down
during bond initialisation.

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