[PATCH] xfrm: Use correct address family in xfrm_state_find

[Steffen Klassert]

On Fri, Sep 25, 2020 at 02:42:56PM +1000, Herbert Xu wrote:
> Resend with proper subject.
>  
> ---8<---
> The struct flowi must never be interpreted by itself as its size
> depends on the address family.  Therefore it must always be grouped
> with its original family value.
> 
> In this particular instance, the original family value is lost in
> the function xfrm_state_find.  Therefore we get a bogus read when
> it's coupled with the wrong family which would occur with inter-
> family xfrm states.
> 
> This patch fixes it by keeping the original family value.
> 
> Note that the same bug could potentially occur in LSM through
> the xfrm_state_pol_flow_match hook.  I checked the current code
> there and it seems to be safe for now as only secid is used which
> is part of struct flowi_common.  But that API should be changed
> so that so that we don't get new bugs in the future.  We could
> do that by replacing fl with just secid or adding a family field.
> 
> Reported-by: syzbot+577fbac3145a6eb2e7a5 at syzkaller.appspotmail.com
> Fixes: 48b8d78315bf ("[XFRM]: State selection update to use inner...")
> Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>

Applied, thanks a lot Herbert!