From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Simon Ser <contact@emersion.fr>
Cc: David Airlie <airlied@linux.ie>,
intel-gfx <intel-gfx@lists.freedesktop.org>,
Randy Dunlap <rdunlap@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
Pekka Paalanen <ppaalanen@gmail.com>
Subject: Re: [Intel-gfx] drm_modes: signed integer overflow
Date: Fri, 23 Oct 2020 18:27:19 +0300 [thread overview]
Message-ID: <20201023152719.GV6112@intel.com> (raw)
In-Reply-To: <BaLsmzqZNUi-nVbYiLstRgspKGlLahAI8vM2_NPfos2PxM0N9lycj-Zn5TdqNtEHB-jeWgmzw9EHJxq4H5552tVi4bAZXTLnP0y1QsTPFtY=@emersion.fr>
On Fri, Oct 23, 2020 at 03:14:20PM +0000, Simon Ser wrote:
> On Thursday, October 22, 2020 12:14 PM, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
>
> > On Wed, Oct 21, 2020 at 08:13:43PM -0700, Randy Dunlap wrote:
> >
> > > Hi,
> > > With linux-next 20201021, when booting up, I am seeing this:
> > > [ 0.560896] UBSAN: signed-integer-overflow in ../drivers/gpu/drm/drm_modes.c:765:20
> > > [ 0.560903] 2376000 * 1000 cannot be represented in type 'int'
> >
> > Dang. Didn't realize these new crazy >8k modes have dotclocks reaching
> > almost 6 GHz, which would overflow even u32. I guess we'll switch to
> > 64bit maths. Now I wonder how many other places can hit this overflow
> > in practice...
>
> Can you provide an example of a full crazy >8k mode?
These are two extreme cases:
/* 216 - 10240x4320@100Hz 64:27 */
{ DRM_MODE("10240x4320", DRM_MODE_TYPE_DRIVER, 5940000, 10240, 12432,
12608, 13200, 0, 4320, 4336, 4356, 4500, 0,
DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC),
.picture_aspect_ratio = HDMI_PICTURE_ASPECT_64_27, },
/* 217 - 10240x4320@120Hz 64:27 */
{ DRM_MODE("10240x4320", DRM_MODE_TYPE_DRIVER, 5940000, 10240, 10528,
10704, 11000, 0, 4320, 4336, 4356, 4500, 0,
DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC),
.picture_aspect_ratio = HDMI_PICTURE_ASPECT_64_27, }
> I'm trying to get
> a fix for my user-space [1], and I'm wondering if int32_t is enough
> after dividing by mode->htotal.
>
> CC Pekka, just FYI (I think Weston has similar code).
>
> [1]: https://github.com/swaywm/wlroots/pull/2450
What's with those 1000000LL constants? Are you storing
clock in Hz units?
--
Ville Syrjälä
Intel
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
WARNING: multiple messages have this Message-ID (diff)
From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Simon Ser <contact@emersion.fr>
Cc: David Airlie <airlied@linux.ie>,
intel-gfx <intel-gfx@lists.freedesktop.org>,
Randy Dunlap <rdunlap@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [Intel-gfx] drm_modes: signed integer overflow
Date: Fri, 23 Oct 2020 18:27:19 +0300 [thread overview]
Message-ID: <20201023152719.GV6112@intel.com> (raw)
In-Reply-To: <BaLsmzqZNUi-nVbYiLstRgspKGlLahAI8vM2_NPfos2PxM0N9lycj-Zn5TdqNtEHB-jeWgmzw9EHJxq4H5552tVi4bAZXTLnP0y1QsTPFtY=@emersion.fr>
On Fri, Oct 23, 2020 at 03:14:20PM +0000, Simon Ser wrote:
> On Thursday, October 22, 2020 12:14 PM, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
>
> > On Wed, Oct 21, 2020 at 08:13:43PM -0700, Randy Dunlap wrote:
> >
> > > Hi,
> > > With linux-next 20201021, when booting up, I am seeing this:
> > > [ 0.560896] UBSAN: signed-integer-overflow in ../drivers/gpu/drm/drm_modes.c:765:20
> > > [ 0.560903] 2376000 * 1000 cannot be represented in type 'int'
> >
> > Dang. Didn't realize these new crazy >8k modes have dotclocks reaching
> > almost 6 GHz, which would overflow even u32. I guess we'll switch to
> > 64bit maths. Now I wonder how many other places can hit this overflow
> > in practice...
>
> Can you provide an example of a full crazy >8k mode?
These are two extreme cases:
/* 216 - 10240x4320@100Hz 64:27 */
{ DRM_MODE("10240x4320", DRM_MODE_TYPE_DRIVER, 5940000, 10240, 12432,
12608, 13200, 0, 4320, 4336, 4356, 4500, 0,
DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC),
.picture_aspect_ratio = HDMI_PICTURE_ASPECT_64_27, },
/* 217 - 10240x4320@120Hz 64:27 */
{ DRM_MODE("10240x4320", DRM_MODE_TYPE_DRIVER, 5940000, 10240, 10528,
10704, 11000, 0, 4320, 4336, 4356, 4500, 0,
DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC),
.picture_aspect_ratio = HDMI_PICTURE_ASPECT_64_27, }
> I'm trying to get
> a fix for my user-space [1], and I'm wondering if int32_t is enough
> after dividing by mode->htotal.
>
> CC Pekka, just FYI (I think Weston has similar code).
>
> [1]: https://github.com/swaywm/wlroots/pull/2450
What's with those 1000000LL constants? Are you storing
clock in Hz units?
--
Ville Syrjälä
Intel
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
WARNING: multiple messages have this Message-ID (diff)
From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Simon Ser <contact@emersion.fr>
Cc: Randy Dunlap <rdunlap@infradead.org>,
David Airlie <airlied@linux.ie>,
intel-gfx <intel-gfx@lists.freedesktop.org>,
LKML <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
Pekka Paalanen <ppaalanen@gmail.com>
Subject: Re: [Intel-gfx] drm_modes: signed integer overflow
Date: Fri, 23 Oct 2020 18:27:19 +0300 [thread overview]
Message-ID: <20201023152719.GV6112@intel.com> (raw)
In-Reply-To: <BaLsmzqZNUi-nVbYiLstRgspKGlLahAI8vM2_NPfos2PxM0N9lycj-Zn5TdqNtEHB-jeWgmzw9EHJxq4H5552tVi4bAZXTLnP0y1QsTPFtY=@emersion.fr>
On Fri, Oct 23, 2020 at 03:14:20PM +0000, Simon Ser wrote:
> On Thursday, October 22, 2020 12:14 PM, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
>
> > On Wed, Oct 21, 2020 at 08:13:43PM -0700, Randy Dunlap wrote:
> >
> > > Hi,
> > > With linux-next 20201021, when booting up, I am seeing this:
> > > [ 0.560896] UBSAN: signed-integer-overflow in ../drivers/gpu/drm/drm_modes.c:765:20
> > > [ 0.560903] 2376000 * 1000 cannot be represented in type 'int'
> >
> > Dang. Didn't realize these new crazy >8k modes have dotclocks reaching
> > almost 6 GHz, which would overflow even u32. I guess we'll switch to
> > 64bit maths. Now I wonder how many other places can hit this overflow
> > in practice...
>
> Can you provide an example of a full crazy >8k mode?
These are two extreme cases:
/* 216 - 10240x4320@100Hz 64:27 */
{ DRM_MODE("10240x4320", DRM_MODE_TYPE_DRIVER, 5940000, 10240, 12432,
12608, 13200, 0, 4320, 4336, 4356, 4500, 0,
DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC),
.picture_aspect_ratio = HDMI_PICTURE_ASPECT_64_27, },
/* 217 - 10240x4320@120Hz 64:27 */
{ DRM_MODE("10240x4320", DRM_MODE_TYPE_DRIVER, 5940000, 10240, 10528,
10704, 11000, 0, 4320, 4336, 4356, 4500, 0,
DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC),
.picture_aspect_ratio = HDMI_PICTURE_ASPECT_64_27, }
> I'm trying to get
> a fix for my user-space [1], and I'm wondering if int32_t is enough
> after dividing by mode->htotal.
>
> CC Pekka, just FYI (I think Weston has similar code).
>
> [1]: https://github.com/swaywm/wlroots/pull/2450
What's with those 1000000LL constants? Are you storing
clock in Hz units?
--
Ville Syrjälä
Intel
next prev parent reply other threads:[~2020-10-23 15:27 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-22 3:13 [Intel-gfx] drm_modes: signed integer overflow Randy Dunlap
2020-10-22 3:13 ` Randy Dunlap
2020-10-22 3:13 ` Randy Dunlap
2020-10-22 10:14 ` [Intel-gfx] " Ville Syrjälä
2020-10-22 10:14 ` Ville Syrjälä
2020-10-22 10:14 ` Ville Syrjälä
2020-10-23 15:14 ` Simon Ser
2020-10-23 15:14 ` Simon Ser
2020-10-23 15:14 ` Simon Ser
2020-10-23 15:27 ` Ville Syrjälä [this message]
2020-10-23 15:27 ` Ville Syrjälä
2020-10-23 15:27 ` Ville Syrjälä
2020-10-23 16:02 ` Simon Ser
2020-10-23 16:02 ` Simon Ser
2020-10-23 16:02 ` Simon Ser
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