From: Wenwen Wang <wang6495@umn.edu>
To: Wenwen Wang <wang6495@umn.edu>
Cc: Kangjie Lu <kjlu@umn.edu>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
viro@zeniv.linux.org.uk,
"open list:STAGING - ATOMISP DRIVER"
<linux-media@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] media: dvb: fix a missing-check bug
Date: Mon, 29 Oct 2018 13:46:04 -0500 [thread overview]
Message-ID: <CAAa=b7ceXdaB9KcZy9ML5pcEwMjYF0ibaB_f6LuuHFe_jSuMYQ@mail.gmail.com> (raw)
In-Reply-To: <1539958334-11531-1-git-send-email-wang6495@umn.edu>
Hello,
Can anyone confirm this bug? Thanks!
Wenwen
On Fri, Oct 19, 2018 at 9:12 AM Wenwen Wang <wang6495@umn.edu> wrote:
>
> In dvb_audio_write(), the first byte of the user-space buffer 'buf' is
> firstly copied and checked to see whether this is a TS packet, which always
> starts with 0x47 for synchronization purposes. If yes, ts_play() will be
> called. Otherwise, dvb_aplay() will be called. In ts_play(), the content of
> 'buf', including the first byte, is copied again from the user space.
> However, after the copy, no check is re-enforced on the first byte of the
> copied data. Given that 'buf' is in the user space, a malicious user can
> race to change the first byte after the check in dvb_audio_write() but
> before the copy in ts_play(). Through this way, the user can supply
> inconsistent code, which can cause undefined behavior of the kernel and
> introduce potential security risk.
>
> This patch adds a necessary check in ts_play() to make sure the first byte
> acquired in the second copy contains the expected value. Otherwise, an
> error code EINVAL will be returned.
>
> Signed-off-by: Wenwen Wang <wang6495@umn.edu>
> ---
> drivers/media/pci/ttpci/av7110_av.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/media/pci/ttpci/av7110_av.c b/drivers/media/pci/ttpci/av7110_av.c
> index ef1bc17..1ff6062 100644
> --- a/drivers/media/pci/ttpci/av7110_av.c
> +++ b/drivers/media/pci/ttpci/av7110_av.c
> @@ -468,6 +468,8 @@ static ssize_t ts_play(struct av7110 *av7110, const char __user *buf,
> }
> if (copy_from_user(kb, buf, TS_SIZE))
> return -EFAULT;
> + if (kb[0] != 0x47)
> + return -EINVAL;
> write_ts_to_decoder(av7110, type, kb, TS_SIZE);
> todo -= TS_SIZE;
> buf += TS_SIZE;
> --
> 2.7.4
>
next prev parent reply other threads:[~2018-10-30 3:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-19 14:12 [PATCH] media: dvb: fix a missing-check bug Wenwen Wang
2018-10-29 18:46 ` Wenwen Wang [this message]
2018-10-30 4:07 ` Bing Bu Cao
2018-11-27 10:43 ` Sean Young
-- strict thread matches above, loose matches on Subject: below --
2018-10-04 14:59 Wenwen Wang
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