netdev - Re: [PATCH] tun: fix mismatch in mutex lock-unlock in tun_get

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Message-Id: <20180219.111500.677838714163586859.davem@davemloft.net>
Date:   Mon, 19 Feb 2018 11:15:00 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     khoroshilov@...ras.ru
Cc:     jasowang@...hat.com, edumazet@...gle.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: Re: [PATCH] tun: fix mismatch in mutex lock-unlock in
 tun_get_user()

From: Alexey Khoroshilov <khoroshilov@...ras.ru>
Date: Sat, 17 Feb 2018 01:11:55 +0300

> There is a single error path where tfile->napi_mutex is left unlocked.
> It can lead to a deadlock.
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>

As Eric explained, tun_napi_frags_enabled() (and therefore 'frags')
will never be true for TUN devices, which is the type handled by this
code path.