Bug#660804: [Bug 42809] New: kernel panic when receiving an ipsec packet

[David Miller <davem@davemloft.net>]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 23 Feb 2012 15:36:26 +0100

> [PATCH] ipsec: be careful of non existing mac headers
> 
> Nicollo Belli reported ipsec crashes in case we handle a frame without
> mac header (atm in his case)
> 
> Before copying mac header, better make sure it is present.
> 
> Bugzilla reference:  https://bugzilla.kernel.org/show_bug.cgi?id=42809
> 
> Reported-by: Niccolò Belli <darkbasic@linuxsystems.it>
> Tested-by: Niccolò Belli <darkbasic@linuxsystems.it>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

Three instances of the same piece of code, maybe a helper function is
appropriate at that point? :-) You might even get ambitious and add a
big comment to that helper function explaining the situation.