Re: [PATCH] rds: fix local ping DoS

[David Miller]

From: Josh Hunt <johunt@xxxxxxxxxx>
Date: Wed, 13 Nov 2013 17:15:43 -0800

> The rds_ib_xmit function in net/rds/ib_send.c in the Reliable Datagram Sockets
> (RDS) protocol implementation allows local users to cause a denial of service
> (BUG_ON and kernel panic) by establishing an RDS connection with the source
> IP address equal to the IPoIB interface's own IP address, as demonstrated by
> rds-ping.
> 
> A local unprivileged user could use this flaw to crash the system.
> 
> CVE-2012-2372
> 
> Reported-by: Honggang Li <honli@xxxxxxxxxx>
> Signed-off-by: Josh Hunt <johunt@xxxxxxxxxx>

I'm sorry I can't apply this.  This commit message needs to be much
less terse and explain things more.

First of all, why is the "off % RDS_FRAG_SIZE" important?

And, even more importantly, why is is OK to avoid this assertion just
because we're going over loopback?

Furthermore, why doesn't net/rds/iw_send.c:rds_iw_xmit() have the same
exact problem?  It makes the same exact assertion check.

I know this RDS code is a steaming pile of poo, but that doesn't mean
we just randomly adjust assertions to make crashes go away without
sufficient understanding of exactly what's going on.

Thanks.
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