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    <body><span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span> changed
          <a class="bz_bug_link 
          bz_status_RESOLVED  bz_closed"
   title="RESOLVED FIXED - i915 "kernel NULL pointer dereference" in kernel-4.18.20"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=108850">bug 108850</a>
          <br>
             <table border="1" cellspacing="0" cellpadding="8">
          <tr>
            <th>What</th>
            <th>Removed</th>
            <th>Added</th>
          </tr>

         <tr>
           <td style="text-align:right;">Status</td>
           <td>NEW
           </td>
           <td>RESOLVED
           </td>
         </tr>

         <tr>
           <td style="text-align:right;">Resolution</td>
           <td>---
           </td>
           <td>FIXED
           </td>
         </tr></table>
      <p>
        <div>
            <b><a class="bz_bug_link 
          bz_status_RESOLVED  bz_closed"
   title="RESOLVED FIXED - i915 "kernel NULL pointer dereference" in kernel-4.18.20"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=108850#c6">Comment # 6</a>
              on <a class="bz_bug_link 
          bz_status_RESOLVED  bz_closed"
   title="RESOLVED FIXED - i915 "kernel NULL pointer dereference" in kernel-4.18.20"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=108850">bug 108850</a>
              from <span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span></b>
        <pre>commit 5179749925933575a67f9d8f16d0cc204f98a29f (HEAD -> drm-intel-next-queued, 
drm-intel/for-linux-next, drm-intel/drm-intel-next-queued)
Author: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Date:   Tue Dec 4 14:15:16 2018 +0000

    drm/i915: Allocate a common scratch page

    Currently we allocate a scratch page for each engine, but since we only
    ever write into it for post-sync operations, it is not exposed to
    userspace nor do we care for coherency. As we then do not care about its
    contents, we can use one page for all, reducing our allocations and
    avoid complications by not assuming per-engine isolation.

    For later use, it simplifies engine initialisation (by removing the
    allocation that required struct_mutex!) and means that we can always rely
    on there being a scratch page.

    v2: Check that we allocated a large enough scratch for I830 w/a

    Fixes: 06e562e7f515 ("drm/i915/ringbuffer: Delay after EMIT_INVALIDATE for
gen4/gen5") # v4.18.20
    Bugzilla: <a class="bz_bug_link 
          bz_status_RESOLVED  bz_closed"
   title="RESOLVED FIXED - i915 "kernel NULL pointer dereference" in kernel-4.18.20"
   href="show_bug.cgi?id=108850">https://bugs.freedesktop.org/show_bug.cgi?id=108850</a>
    Signed-off-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
    Cc: Tvrtko Ursulin <<a href="mailto:tvrtko.ursulin@intel.com">tvrtko.ursulin@intel.com</a>>
    Cc: Mika Kuoppala <<a href="mailto:mika.kuoppala@linux.intel.com">mika.kuoppala@linux.intel.com</a>>
    Reviewed-by: Mika Kuoppala <<a href="mailto:mika.kuoppala@linux.intel.com">mika.kuoppala@linux.intel.com</a>>
    Link:
<a href="https://patchwork.freedesktop.org/patch/msgid/20181204141522.13640-1-chris@chris-wilson.co.uk">https://patchwork.freedesktop.org/patch/msgid/20181204141522.13640-1-chris@chris-wilson.co.uk</a>
    Cc: Joonas Lahtinen <<a href="mailto:joonas.lahtinen@linux.intel.com">joonas.lahtinen@linux.intel.com</a>>
    Cc: <<a href="mailto:stable@vger.kernel.org">stable@vger.kernel.org</a>> # v4.18.20+

should apply to v4.18 (and be auto-backported) and prevent the NULL deref.</pre>
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