Hi Deepak Am 18.03.19 um 17:59 schrieb Deepak Singh Rawat: > Hi Thomas, > > Thanks for doing this and somehow I missed the last patch, sorry about > that. Have some questions below otherwise the patch looks good to me. > > Reviewed-by: Deepak Rawat <dra...@vmware.com> > > I will include your changes in vmwgfx-next and run tests.
Thank you.
>
> On Mon, 2019-03-18 at 15:47 +0100, Thomas Zimmermann wrote:
>> When calling vmw_fb_set_par(), the mode stored in par->set_mode gets
>> free'd
>> twice. The first free is in vmw_fb_kms_detach(), the second is near
>> the
>> end of vmw_fb_set_par() under the name of 'old_mode'. The mode-
>> setting code
>> only works correctly if the mode doesn't actually change.
>
> You mean to say that without your patch vmwgfx fb driver fail to change
> the mode?
Yes. It's hard to trigger as the usual resolution always appears to be
800x600. We (SUSE) have a customer with a custom X11 modeline setting,
which sets the resolution to something different. In this case, the
double-free bug happens.
>
>> Removing 'old_mode'
>> in favor of using par->set_mode directly fixes the problem.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
>> ---
>> drivers/gpu/drm/vmwgfx/vmwgfx_fb.c | 12 +++---------
>> 1 file changed, 3 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fb.c
>> b/drivers/gpu/drm/vmwgfx/vmwgfx_fb.c
>> index b913a56f3426..2a9112515f46 100644
>> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_fb.c
>> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fb.c
>> @@ -564,11 +564,9 @@ static int vmw_fb_set_par(struct fb_info *info)
>> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>> DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_PVSYNC)
>> };
>> - struct drm_display_mode *old_mode;
>> struct drm_display_mode *mode;
>> int ret;
>>
>> - old_mode = par->set_mode;
>> mode = drm_mode_duplicate(vmw_priv->dev, &new_mode);
>> if (!mode) {
>> DRM_ERROR("Could not create new fb mode.\n");
>> @@ -579,11 +577,7 @@ static int vmw_fb_set_par(struct fb_info *info)
>> mode->vdisplay = var->yres;
>> vmw_guess_mode_timing(mode);
>>
>> - if (old_mode && drm_mode_equal(old_mode, mode)) {
>> - drm_mode_destroy(vmw_priv->dev, mode);
>> - mode = old_mode;
>> - old_mode = NULL;
>
> I am having hard time understanding original intention for this piece
> of code. Was there a restriction to send pointer to old mode if mode
> were same and that restriction don't hold anymore. Sorry I am not
> familiar with this code area.
Hmm, I can only guess about motivation: it looks like the author wanted
to keep the original value of 'par->set_mode' unless the mode really
changes. But it doesn't make a difference whether the pointer's value
changes or not.
Best regards
Thomas
>
>> - } else if (!vmw_kms_validate_mode_vram(vmw_priv,
>> + if (!vmw_kms_validate_mode_vram(vmw_priv,
>> mode->hdisplay *
>> DIV_ROUND_UP(var-
>>> bits_per_pixel, 8),
>> mode->vdisplay)) {
>> @@ -620,8 +614,8 @@ static int vmw_fb_set_par(struct fb_info *info)
>> schedule_delayed_work(&par->local_work, 0);
>>
>> out_unlock:
>> - if (old_mode)
>> - drm_mode_destroy(vmw_priv->dev, old_mode);
>> + if (par->set_mode)
>> + drm_mode_destroy(vmw_priv->dev, par->set_mode);
>> par->set_mode = mode;
>>
>> mutex_unlock(&par->bo_mutex);
>> --
>> 2.20.1
>>
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--
Thomas Zimmermann
Graphics Driver Developer
SUSE Linux GmbH, Maxfeldstr. 5, D-90409 Nürnberg
Tel: +49-911-74053-0; Fax: +49-911-7417755; https://www.suse.com/
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard,
Graham Norton, HRB 21284 (AG Nürnberg)
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