[Bug 99231] [HSW][i965] Crash in upload_3dstate_streamout()

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Fri Dec 30 23:48:34 UTC 2016


https://bugs.freedesktop.org/show_bug.cgi?id=99231

Kenneth Graunke <kenneth at whitecape.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED
           Assignee|intel-3d-bugs at lists.freedes |kenneth at whitecape.org
                   |ktop.org                    |

--- Comment #4 from Kenneth Graunke <kenneth at whitecape.org> ---
Turns out it was different breakage.

Should be fixed by:

commit 62a819184141133478cfdcfa76b62d5bb7e14fd5
Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Fri Dec 30 15:35:02 2016 -0800

    i965: Avoid NULL pointer dereference when transform feedback is off.

    upload_3dstate_streamout can be called when there's no currently bound
    transform feedback object.  In this case, we get the default object,
    which has a NULL shader (previously gl_shader_program, now gl_program).

    The old code did something sketchy, but which worked:

       const struct gl_transform_feedback_info *linked_xfb_info =
          &xfb_obj->shader_program->LinkedTransformFeedback;

    Here, if shader_program is NULL, this would be a bogus pointer of 0x60.
    But we never actually dereferenced it, so it worked out.

    With Timothy's recent reworks, we actually end up dereferencing
    xfb_obj->program along the way, which crashes since it's NULL.

    The solution is to move this pointer initialization into the "active"
    block, where we know it actually exists and won't be bogus.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99231
    Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
    Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
    Reviewed-by: Timothy Arceri <timothy.arceri at collabora.com>

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