instant oops with AF_ROSE

instant oops with AF_ROSE

[David Miller]

The support for ipv4 over rose devices has been broken for as long as
the code has existed (I went back to 2.0.x just to make sure).  Try
this:

modprobe rose
ip link set rose0 up
ip addr add 11.0.0.3/8 dev rose0
ping -b 11.255.255.255

That should crash your box pretty well.

The immediate reason is that rose_rebuild_header() calls
rose_route_frame() with second arg NULL.

The first thing rose_route_frame() does is take that second arg and
dereference it in order to find the appropriate rose neighbour to use.

Again, it has "worked" this way since day one.  Ie. it never worked.

Since this has never worked, I think the thing to do is to simply
remove all of the rose device code.  It's only used to provide support
for ipv4 over ROSE and it simply never worked.

If someone wants to resurrect this, that's fine, but they'll have
to implement proper header_ops and a real transmit function instead
of the hacky thing it does now where it does the transmit in the
header building routines :-/

Re: instant oops with AF_ROSE

[Chuck Hast]

On Wed, Jul 6, 2011 at 06:57, David Miller <davem@davemloft.net> wrote:
>
> The support for ipv4 over rose devices has been broken for as long as
> the code has existed (I went back to 2.0.x just to make sure).  Try
> this:
>
> modprobe rose
> ip link set rose0 up
> ip addr add 11.0.0.3/8 dev rose0
> ping -b 11.255.255.255
>
> That should crash your box pretty well.
>
----- Text cut for bandwidth reduction-----------

It has been a while, and we were (still are I just am not active)  using FPAC
we have run a lot of IP through it, and never seemed to have a issue, but
perhaps this is not quite in that area.

I  am sure Bernard will see this and pitch in with more info. I am
just trying to
figure out if we are taking two different pieces here.

Here in FL I have ran both NetRom and IP over ROSE through FPAC boxes
with no issues that I can remember. FPAC is a wrapper around the rose piece.
We probably have people still doing IP inside ROSE through FPAC boxes around
the state, not sure who or where, but it would not be a surprise to me because
some use SMTP between their BBS devices.


Bernard, any comments?
-- 

Chuck Hast  -- KP4DJT --
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Re: instant oops with AF_ROSE

[Bernard F6BVP]

Hi,

What we do with ROSE nodes is to create a network allowing AX25 frames 
routing based on destination address. However, basically, ROSE frames
are still AX.25 standard frames that can be sent over packet radio.
In order to relay rose frames through Internet, applications like 
ax25ipd encapsulates rose inside of IP or UDP frames.

I agree that rose module is still unfriendly and will crash linux kernel 
on some occasions.
For example, after creating rose socket and populating rose routing 
table, removing rose module is not possible.

There is either a kernel crash or a looping message

kernel:unregister_netdevice: waiting for rose0 to become free. Usage 
count = 6

where count can be any number without any relation to actual usage
and remaining the same, preventing Linux to shutdown.

I noticed that there are no refcount entries in rose node or rose neigh
structures. This may be related ?


Bernard, f6bvp



Chuck Hast wrote :

It has been a while, and we were (still are I just am not active)  using 
FPAC
we have run a lot of IP through it, and never seemed to have a issue, but
perhaps this is not quite in that area.

I  am sure Bernard will see this and pitch in with more info. I am
just trying to
figure out if we are taking two different pieces here.

Here in FL I have ran both NetRom and IP over ROSE through FPAC boxes
with no issues that I can remember. FPAC is a wrapper around the rose piece.
We probably have people still doing IP inside ROSE through FPAC boxes around
the state, not sure who or where, but it would not be a surprise to me 
because
some use SMTP between their BBS devices.


Bernard, any comments?

Re: instant oops with AF_ROSE

[Ralf Baechle]

On Sat, Jul 09, 2011 at 05:05:09PM +0200, Bernard F6BVP wrote:

> What we do with ROSE nodes is to create a network allowing AX25
> frames routing based on destination address. However, basically,
> ROSE frames
> are still AX.25 standard frames that can be sent over packet radio.
> In order to relay rose frames through Internet, applications like
> ax25ipd encapsulates rose inside of IP or UDP frames.
> 
> I agree that rose module is still unfriendly and will crash linux
> kernel on some occasions.
> For example, after creating rose socket and populating rose routing
> table, removing rose module is not possible.
> 
> There is either a kernel crash or a looping message
> 
> kernel:unregister_netdevice: waiting for rose0 to become free. Usage
> count = 6
> 
> where count can be any number without any relation to actual usage
> and remaining the same, preventing Linux to shutdown.
> 
> I noticed that there are no refcount entries in rose node or rose neigh
> structures. This may be related ?

As part of fixing the problem reported by David I've found 4 race conditions
so far.  I've posted the patches to linux-hams for testing but on a 2nd
thought I think the race accessing rose_neigh->use is unlikely to be the
cause for what Bernard is observing.

  Ralf