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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 - NULL dereference in GfxState.cc:6127"
href="https://bugs.freedesktop.org/show_bug.cgi?id=101504">101504</a>
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<th>Summary</th>
<td>NULL dereference in GfxState.cc:6127
</td>
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<th>Product</th>
<td>poppler
</td>
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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>
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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>poppler-bugs@lists.freedesktop.org
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<th>Reporter</th>
<td>foca@salesforce.com
</td>
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<pre>Created <span class=""><a href="attachment.cgi?id=132068" name="attach_132068" title="Proof of concept">attachment 132068</a> <a href="attachment.cgi?id=132068&action=edit" title="Proof of concept">[details]</a></span>
Proof of concept
There is a NULL dereference in GfxState.cc:6127.
The function drawSoftMaskedImage calls getLine() at CairoOutputDev.cc:2710
which returns NULL, and stores that in pix. The value is than passed on to the
getGrayLine function which tries to dereference it, resulting in a null
dereference.
2708 for (y = 0; y < maskHeight; y++) {
2709 maskDest = (unsigned char *) (maskBuffer + y * row_stride);
2710 pix = maskImgStr->getLine();
2711 maskColorMap->getGrayLine (pix, maskDest, maskWidth);
2712 }
The reason NULL is returned by getLine due to the following
`ImageStream::getLine`
529 if (unlikely(inputLine == NULL)) {
530 return NULL;
531 }
At the point inp is set to whatever pix was( pix=in), in our case pix was NULL.
On line 6127 the dereference takes place and poppler crashes trying to
dereference a NULL pointer.
6123 default:
6124 inp = in;
6125 for (j = 0; j < length; j++)
6126 for (i = 0; i < nComps; i++) {
6127 *inp = byte_lookup[*inp * nComps + i];
6128 inp++;
6129 }
A solution could be an additional check at CairoOutputDev.cc:2710 to check the
line isn't NULL:
2710 pix = maskImgStr->getLine();
2711 if (pix == NULL) continue;
2712 maskColorMap->getGrayLine (pix, maskDest, maskWidth);
PoC is attached.
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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