linux-kernel - Re: [PATCH] bluetooth: 6lowpan: fix use after free in chan

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Date:   Fri, 31 Mar 2017 12:10:27 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Michael Scott <michael.scott@...aro.org>
Cc:     "Gustavo F. Padovan" <gustavo@...ovan.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jukka Rissanen <jukka.rissanen@...ux.intel.com>,
        linux-bluetooth@...r.kernel.org, linux-wpan@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bluetooth: 6lowpan: fix use after free in
 chan_suspend/resume

Hi Michael,

> A status field in the skb_cb struct was storing a channel status
> based on channel suspend/resume events.  This stored status was
> then used to return EAGAIN if there were packet sending issues
> in snd_pkt().
> 
> The issue is that the skb has been freed by the time the callback
> to 6lowpan's suspend/resume was called.  So, this generates a
> "use after free" issue that was noticed while running kernel tests
> with KASAN debug enabled.
> 
> Let's eliminate the status field entirely as we can use the channel
> tx_credits to indicate whether we should return EAGAIN when handling
> packets.
> 
> Signed-off-by: Michael Scott <michael.scott@...aro.org>
> ---
> net/bluetooth/6lowpan.c | 21 +++------------------
> 1 file changed, 3 insertions(+), 18 deletions(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel