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drm/modes: Avoid divide by zero harder in drm_mode_vrefresh()

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commit 9398332f23 upstream.

drm_mode_vrefresh() is trying to avoid divide by zero
by checking whether htotal or vtotal are zero. But we may
still end up with a div-by-zero of vtotal*htotal*...

Cc: stable@vger.kernel.org
Reported-by: syzbot+622bba18029bcde672e1@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=622bba18029bcde672e1
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241129042629.18280-2-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ville Syrjälä
2024-11-29 06:26:28 +02:00
committed by Greg Kroah-Hartman
parent d1b96495fa
commit b39de5a71b
1 changed files with 7 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/gpu/drm/drm_modes.c
+7 -4
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@@ -1285,14 +1285,11 @@ EXPORT_SYMBOL(drm_mode_set_name);
*/
int drm_mode_vrefresh(const struct drm_display_mode *mode)
{
unsigned int num, den;
unsigned int num = 1, den = 1;
if (mode->htotal == 0 || mode->vtotal == 0)
return 0;
num = mode->clock;
den = mode->htotal * mode->vtotal;
if (mode->flags & DRM_MODE_FLAG_INTERLACE)
num *= 2;
if (mode->flags & DRM_MODE_FLAG_DBLSCAN)
@@ -1300,6 +1297,12 @@ int drm_mode_vrefresh(const struct drm_display_mode *mode)
if (mode->vscan > 1)
den *= mode->vscan;
if (check_mul_overflow(mode->clock, num, &num))
return 0;
if (check_mul_overflow(mode->htotal * mode->vtotal, den, &den))
return 0;
return DIV_ROUND_CLOSEST_ULL(mul_u32_u32(num, 1000), den);
}
EXPORT_SYMBOL(drm_mode_vrefresh);