linux-kernel - Re: [Tee-dev] [PATCH] tee: shm: fix use-after-free via temporarily dropped reference

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Message-ID: <CAOcqxo3B1WYvrRqCVw=bDXFBwcCWQcPm3TT1XQB=NcahPcwEUA@mail.gmail.com>
Date:   Mon, 7 May 2018 17:54:02 +0300
From:   Volodymyr Babchuk <vlad.babchuk@...il.com>
To:     Jens Wiklander <jens.wiklander@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        tee-dev@...ts.linaro.org, Jann Horn <jannh@...gle.com>
Subject: Re: [Tee-dev] [PATCH] tee: shm: fix use-after-free via temporarily
 dropped reference

Hi Jens,

On 7 May 2018 at 12:58, Jens Wiklander <jens.wiklander@...aro.org> wrote:
> From: Jann Horn <jannh@...gle.com>
>
> Bump the file's refcount before moving the reference into the fd table,
> not afterwards. The old code could drop the file's refcount to zero for a
> short moment before calling get_file() via get_dma_buf().
>
> This code can only be triggered on ARM systems that use Linaro's OP-TEE.
>
> Fixes: 967c9cca2cc5 ("tee: generic TEE subsystem")
> Signed-off-by: Jann Horn <jannh@...gle.com>
> Signed-off-by: Jens Wiklander <jens.wiklander@...aro.org>
Reviewed-by: Volodymyr Babchuk <vlad.babchuk@...il.com>

-- 
WBR Volodymyr Babchuk aka lorc [+380976646013]
mailto: vlad.babchuk@...il.com