Re: [PATCH net] net: esp{4,6}: fix potential MTU calculation overflows

[David Miller <davem@davemloft.net>]

From: Daniel Borkmann <dborkman@redhat.com>
Date: Mon,  5 Aug 2013 12:49:35 +0200

> Commit 91657eafb ("xfrm: take net hdr len into account for esp payload
> size calculation") introduced a possible interger overflow in
> esp{4,6}_get_mtu() handlers in case of x->props.mode equals
> XFRM_MODE_TUNNEL. Thus, the following expression will overflow
> 
>   unsigned int net_adj;
>   ...
>   <case ipv{4,6} XFRM_MODE_TUNNEL>
>          net_adj = 0;
>   ...
>   return ((mtu - x->props.header_len - crypto_aead_authsize(esp->aead) -
>            net_adj) & ~(align - 1)) + (net_adj - 2);
> 
> where (net_adj - 2) would be evaluated as <foo> + (0 - 2) in an unsigned
> context. Fix it by simply removing brackets as those operations here
> do not need to have special precedence.
> 
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

Applied.