netdev - [PATCH] fix for initial link state in 2.6.28

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 1 Jan 2009 18:12:59 -0500
From:	"Michael Marineau" <mike@...ineau.org>
To:	netdev@...r.kernel.org
Subject: [PATCH] fix for initial link state in 2.6.28

Greetings,

Commit b47300168e770b60ab96c8924854c3b0eb4260eb "Do not fire linkwatch
events until the device is registered." was made as a workaround for
drivers that call netif_carrier_off before registering the device.
Unfortunately this causes these drivers to incorrectly report their
link status as IF_OPER_UNKNOWN which can falsely set the IFF_RUNNING
flag when the interface is first brought up. This issues was
previously pointed out[1] but was dismissed saying that IFF_RUNNING is
not related to the link status. From my digging IFF_RUNNING, as
reported to userspace, is based on the link state. It is set based on
__LINK_STATE_START and IF_OPER_UP or IF_OPER_UNKNOWN. See [2], [3],
and [4]. (Whether or not the kernel has IFF_RUNNING set in flags is
not reported to user space so it may well be independent of the link,
I don't know if and when it may get set.)

The end result depends slightly depending on the driver. The the two I
tested were e1000e and b44. With e1000e if the system is booted
without a network cable attached the interface will falsely report
RUNNING when it is brought up causing NetworkManager to attempt to
start it and eventually time out. With b44 when the system is booted
with a network cable attached and brought up with dhcpcd it will time
out the first time.

The attached patch that will still set the operstate variable
correctly to IF_OPER_UP/DOWN/etc when linkwatch_fire_event is called
but then return rather than skipping the linkwatch_fire_event call
entirely as the previous fix did. (sorry it isn't inline, I don't have
a patch friendly email client at the moment)

What ever the final fix for this is, it should probably be pushed into
the stable tree since this is a minor but annoying regression in
2.6.28.

[1] http://marc.info/?l=linux-netdev&m=122922534630000&w=2
[2] http://lxr.linux.no/linux+v2.6.28/net/core/dev.c#L3349
[3] http://lxr.linux.no/linux+v2.6.28/include/linux/netdevice.h#L1147
[4] http://lxr.linux.no/linux+v2.6.28/include/linux/netdevice.h#L1376

Cheers,
-- 
Michael Marineau
mike@...ineau.org

View attachment "operstate-fix.patch" of type "text/x-patch" (1493 bytes)