netdev - Re: [PATCH net] soreuseport: fix initialization race

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Date:   Sun, 22 Oct 2017 02:04:26 +0100 (WEST)
From:   David Miller <davem@...emloft.net>
To:     kraigatgoog@...il.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net] soreuseport: fix initialization race

From: Craig Gallek <kraigatgoog@...il.com>
Date: Thu, 19 Oct 2017 15:00:29 -0400

> From: Craig Gallek <kraig@...gle.com>
> 
> Syzkaller stumbled upon a way to trigger
> WARNING: CPU: 1 PID: 13881 at net/core/sock_reuseport.c:41
> reuseport_alloc+0x306/0x3b0 net/core/sock_reuseport.c:39
> 
> There are two initialization paths for the sock_reuseport structure in a
> socket: Through the udp/tcp bind paths of SO_REUSEPORT sockets or through
> SO_ATTACH_REUSEPORT_[CE]BPF before bind.  The existing implementation
> assumedthat the socket lock protected both of these paths when it actually
> only protects the SO_ATTACH_REUSEPORT path.  Syzkaller triggered this
> double allocation by running these paths concurrently.
> 
> This patch moves the check for double allocation into the reuseport_alloc
> function which is protected by a global spin lock.
> 
> Fixes: e32ea7e74727 ("soreuseport: fast reuseport UDP socket selection")
> Fixes: c125e80b8868 ("soreuseport: fast reuseport TCP socket selection")
> Signed-off-by: Craig Gallek <kraig@...gle.com>

Applied and queued up for -stable.