netdev - Re: [PATCH net] inetpeer: fix uninit-value in inet

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Message-Id: <20180409.105839.445341256424332032.davem@davemloft.net>
Date:   Mon, 09 Apr 2018 10:58:39 -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] inetpeer: fix uninit-value in inet_getpeer

From: Eric Dumazet <edumazet@...gle.com>
Date: Mon,  9 Apr 2018 06:43:27 -0700

> syzbot/KMSAN reported that p->dtime was read while it was
> not yet initialized in :
> 
> 	delta = (__u32)jiffies - p->dtime;
> 	if (delta < ttl || !refcount_dec_if_one(&p->refcnt))
> 		gc_stack[i] = NULL;
> 
> This is a false positive, because the inetpeer wont be erased
> from rb-tree if the refcount_dec_if_one(&p->refcnt) does not
> succeed. And this wont happen before first inet_putpeer() call
> for this inetpeer has been done, and ->dtime field is written
> exactly before the refcount_dec_and_test(&p->refcnt).
> 
> The KMSAN report was :
 ...
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied, but it looks like we are just adding assignments simply
to placate these reports when the tools and facilities cannot
see through the logic properly.