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      <base href="https://bugs.freedesktop.org/" />
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - weston-launch -u doesn't work"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=65933">65933</a>
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>wayland-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>weston-launch -u doesn't work
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>ross@burtonini.com
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Other
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>weston
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>Wayland
          </td>
        </tr></table>
      <p>
        <div>
        <pre>When weston-launch is used as root with the -u option to switch to a non-root
user, the supplementary group list isn't set so this user is a member of root's
group and the primary group of the user (in my situation, the group list is
"root xuser").

This doesn't work too well when permissions on /dev/dri/card0 are root:video
660, because this user isn't currently a member of video (despite /etc/group
saying otherwise).  Permission denied, weston fails.

It looks like the solution on Linux would be to use getgrouplist()/setgroups()
before setgid()/setuid().</pre>
        </div>
      </p>
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