netdev - Re: [PATCH net] bpf: fix branch offset adjustment on backjumps after patching ctx expansion

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Message-Id: <20160210.170212.1863380328830638787.davem@davemloft.net>
Date:	Wed, 10 Feb 2016 17:02:12 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	daniel@...earbox.net
Cc:	alexei.starovoitov@...il.com, elena.reshetova@...el.com,
	eric.dumazet@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] bpf: fix branch offset adjustment on backjumps
 after patching ctx expansion

From: Daniel Borkmann <daniel@...earbox.net>
Date: Wed, 10 Feb 2016 16:47:11 +0100

> When ctx access is used, the kernel often needs to expand/rewrite
> instructions, so after that patching, branch offsets have to be
> adjusted for both forward and backward jumps in the new eBPF program,
> but for backward jumps it fails to account the delta. Meaning, for
> example, if the expansion happens exactly on the insn that sits at
> the jump target, it doesn't fix up the back jump offset.
 ...
> Fixes: 9bac3d6d548e ("bpf: allow extended BPF programs access skb fields")
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>

Applied and queued up for -stable, thanks Daniel.