Messages in this thread | | | Subject | Re: [Linux-kernel-mentees] [PATCH] v4l2-tpg: Fix global-out-of-bounds read in precalculate_color() | From | Hans Verkuil <> | Date | Wed, 19 Aug 2020 16:26:28 +0200 |
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Hi Peilin,
On 10/08/2020 07:05, Peilin Ye wrote: > precalculate_color() is reading out of `sin` since `tpg->hue` is not being > properly checked. Fix it. `cos` is safe, as long as `tpg->hue` is higher > than or equal to -192.
Thank you for this patch, but there is something I don't understand, namely just *how* tpg->hue can be out-of-range.
From what I can see vivid sets hue via tpg_s_hue() when the V4L2_CID_HUE control is set. But that control has a range of -128...128, so ctrl->val should always be in that range.
I would really like to know 1) what the value of tpg->hue actually is when it goes out of range, and 2) who is changing it to that value. Can you do a bit more digging?
That said, it makes sense that precalculate_color() avoids reading out-of-bounds.
> > Fixes: 63881df94d3e ("[media] vivid: add the Test Pattern Generator") > Reported-and-tested-by: syzbot+02d9172bf4c43104cd70@syzkaller.appspotmail.com > Link: https://syzkaller.appspot.com/bug?id=db50123c788e2cc5a9d90de569c398b66293ee48 > Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com> > --- > drivers/media/common/v4l2-tpg/v4l2-tpg-core.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c > index 50f1e0b28b25..52205fe096f7 100644 > --- a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c > +++ b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c > @@ -930,6 +930,9 @@ static void precalculate_color(struct tpg_data *tpg, int k) > /* Implement these operations */ > int tmp_cb, tmp_cr; > > + if (tpg->hue < -128 || tpg->hue > 128) > + return;
Rather than returning here, I prefer to just clamp tpg->hue to the valid range.
I'd be willing to merge a patch that clamps tpg->hue (it certainly doesn't hurt), but I also would like to understand how it can be out of range in the first place. I have the feeling that this is a symptom of another problem elsewhere.
Regards,
Hans
> + > /* First convert to YCbCr */ > > color_to_ycbcr(tpg, r, g, b, &y, &cb, &cr); >
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