linux-kernel - Re: [PATCH v4 4/4] media: venus: hfi: add a check to handle OOB in sfr region

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Message-ID: <CAAFQd5ABR8BwG_9JVPzzp+HZv6O=B9r-ipjKQHku7DdTGASetQ@mail.gmail.com>
Date: Fri, 21 Feb 2025 12:55:23 +0900
From: Tomasz Figa <tfiga@...omium.org>
To: Vikash Garodia <quic_vgarodia@...cinc.com>
Cc: Hans Verkuil <hverkuil@...all.nl>, Stanimir Varbanov <stanimir.k.varbanov@...il.com>, 
	"Bryan O'Donoghue" <bryan.odonoghue@...aro.org>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Hans Verkuil <hans.verkuil@...co.com>, Stanimir Varbanov <stanimir.varbanov@...aro.org>, 
	Mauro Carvalho Chehab <mchehab+samsung@...nel.org>, Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
	linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v4 4/4] media: venus: hfi: add a check to handle OOB in
 sfr region

On Fri, Feb 21, 2025 at 12:56 AM Vikash Garodia
<quic_vgarodia@...cinc.com> wrote:
>
>
> On 2/20/2025 8:53 PM, Hans Verkuil wrote:
> > On 2/7/25 09:24, Vikash Garodia wrote:
> >> sfr->buf_size is in shared memory and can be modified by malicious user.
> >> OOB write is possible when the size is made higher than actual sfr data
> >> buffer. Cap the size to allocated size for such cases.
> >>
> >> Cc: stable@...r.kernel.org
> >> Fixes: d96d3f30c0f2 ("[media] media: venus: hfi: add Venus HFI files")
> >> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> >> Signed-off-by: Vikash Garodia <quic_vgarodia@...cinc.com>
> >> ---
> >>  drivers/media/platform/qcom/venus/hfi_venus.c | 9 +++++++--
> >>  1 file changed, 7 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/media/platform/qcom/venus/hfi_venus.c b/drivers/media/platform/qcom/venus/hfi_venus.c
> >> index 6b615270c5dae470c6fad408c9b5bc037883e56e..c3113420d266e61fcab44688580288d7408b50f4 100644
> >> --- a/drivers/media/platform/qcom/venus/hfi_venus.c
> >> +++ b/drivers/media/platform/qcom/venus/hfi_venus.c
> >> @@ -1041,18 +1041,23 @@ static void venus_sfr_print(struct venus_hfi_device *hdev)
> >>  {
> >>      struct device *dev = hdev->core->dev;
> >>      struct hfi_sfr *sfr = hdev->sfr.kva;
> >> +    u32 size;
> >>      void *p;
> >>
> >>      if (!sfr)
> >>              return;
> >>
> >> -    p = memchr(sfr->data, '\0', sfr->buf_size);
> >> +    size = sfr->buf_size;
> >
> > If this is ever 0...
> >
> >> +    if (size > ALIGNED_SFR_SIZE)
> >> +            size = ALIGNED_SFR_SIZE;
> >> +
> >> +    p = memchr(sfr->data, '\0', size);
> >>      /*
> >>       * SFR isn't guaranteed to be NULL terminated since SYS_ERROR indicates
> >>       * that Venus is in the process of crashing.
> >>       */
> >>      if (!p)
> >> -            sfr->data[sfr->buf_size - 1] = '\0';
> >> +            sfr->data[size - 1] = '\0';
> >
> > ...then this will overwrite memory. It probably can't be 0, but a check or perhaps
> > just a comment might be good. It looks a bit scary.
> Thats correct, it would not be 0 as its a prefixed one [1]. I can put up a
> comment here.

Couldn't a bug (or vulnerability) in the firmware actually still cause
it to write 0 there?

>
> [1]
> https://elixir.bootlin.com/linux/v6.14-rc3/source/drivers/media/platform/qcom/venus/hfi_venus.c#L836
> >
> > Regards,
> >
> >       Hans
> >
> >>
> >>      dev_err_ratelimited(dev, "SFR message from FW: %s\n", sfr->data);
> >>  }
> >>
> Regards,
> Vikash