Bug 101530 - Attempting free on address which was not malloc() in cairo-clip.c:137
Summary: Attempting free on address which was not malloc() in cairo-clip.c:137
Alias: None
Product: cairo
Classification: Unclassified
Component: general (show other bugs)
Version: unspecified
Hardware: Other All
: medium normal
Assignee: Chris Wilson
QA Contact: cairo-bugs mailing list
Depends on:
Reported: 2017-06-20 21:04 UTC by foca@salesforce.com
Modified: 2018-08-25 13:31 UTC (History)
0 users

See Also:
i915 platform:
i915 features:

Proof of concept (5.35 KB, application/pdf)
2017-06-20 21:04 UTC, foca@salesforce.com

Description foca@salesforce.com 2017-06-20 21:04:07 UTC
Created attachment 132101 [details]
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;
133	    if (clip->path != NULL)
134		_cairo_clip_path_destroy (clip->path);
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;
158	    if (clip == NULL) {
159		clip = _cairo_clip_create ();
160		if (clip == NULL)
161		    return _cairo_clip_set_all_clipped (clip);
162	    }
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_)
Comment 1 GitLab Migration User 2018-08-25 13:31:54 UTC
-- GitLab Migration Automatic Message --

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