netdev - Re: [PATCH net 0/8] net: fix uninit-values in networking stack

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Message-Id: <20180407.224025.1923207101579714958.davem@davemloft.net>
Date:   Sat, 07 Apr 2018 22:40:25 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net 0/8] net: fix uninit-values in networking stack

From: Eric Dumazet <edumazet@...gle.com>
Date: Sat,  7 Apr 2018 13:42:35 -0700

> It seems syzbot got new features enabled, and fired some interesting
> reports. Oh well.

Series applied, however in patch #7 the condition syzbot detects
cannot happen.

In all code paths that lead to __mkroute_output() with res->type
uninitialized, __mkroute_output() will reassign the local variable
'type' before reading it.

Furthermore, by doing a full structure initialization lots of
unrelated things will be initialized now as well.

We explicitly are only setting up the "inputs" of the fib_result
object before we call fib_lookup().  The prefixlen and other members
have no business being initialized there.