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<base href="https://bugs.freedesktop.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Attempting free on address which was not malloc() in cairo-clip.c:137"
href="https://bugs.freedesktop.org/show_bug.cgi?id=101530">101530</a>
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<th>Summary</th>
<td>Attempting free on address which was not malloc() in cairo-clip.c:137
</td>
</tr>
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<th>Product</th>
<td>cairo
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>Other
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
</td>
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<th>Component</th>
<td>general
</td>
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<th>Assignee</th>
<td>chris@chris-wilson.co.uk
</td>
</tr>
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<th>Reporter</th>
<td>foca@salesforce.com
</td>
</tr>
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<th>QA Contact</th>
<td>cairo-bugs@cairographics.org
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<pre>Created <span class=""><a href="attachment.cgi?id=132101" name="attach_132101" title="Proof of concept">attachment 132101</a> <a href="attachment.cgi?id=132101&action=edit" title="Proof of concept">[details]</a></span>
Proof of concept
There is a bug attempting free on address which was not malloc() in
cairo-clip.c:137:
127 void
128 _cairo_clip_destroy (cairo_clip_t *clip)
129 {
130 if (clip == NULL || _cairo_clip_is_all_clipped (clip))
131 return;
132
133 if (clip->path != NULL)
134 _cairo_clip_path_destroy (clip->path);
135
136 if (clip->boxes != &clip->embedded_box)
137 free (clip->boxes);
In some cases clip->boxes could be allocated but in the PoC is not allocated is
assigned to clip->embedded_box a member of the same class at
cairo-clip-boxes.c:165
149 static cairo_clip_t *
150 _cairo_clip_intersect_rectangle_box (cairo_clip_t *clip,
151 const cairo_rectangle_int_t *r,
152 const cairo_box_t *box)
153 {
154 cairo_box_t extents_box;
155 cairo_bool_t changed = FALSE;
156 int i, j;
157
158 if (clip == NULL) {
159 clip = _cairo_clip_create ();
160 if (clip == NULL)
161 return _cairo_clip_set_all_clipped (clip);
162 }
163
164 if (clip->num_boxes == 0) {
165 clip->boxes = &clip->embedded_box;
There is already a check in _cairo_clip_destroy to avoid similar cases:
136 if (clip->boxes != &clip->embedded_box)
But with the PoC the clip where the embedded_box is comming is different the
the clip being destroyed.
This bug was found when using a poppler util, pdftocairo. A PoC is attached. To
reproduce the bug use:
pdftocairo -svg PoC.pdf
This vulnerability has been found by Offensive Research at Salesforce.com:
Alberto Garcia (@algillera), Francisco Oca (@francisco_oca) & Suleman Ali
(@Salbei_)</pre>
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