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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Find size_t overflows in calls to malloc, realloc"
href="https://llvm.org/bugs/show_bug.cgi?id=27729">27729</a>
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<th>Summary</th>
<td>Find size_t overflows in calls to malloc, realloc
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>Macintosh
</td>
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<th>OS</th>
<td>MacOS X
</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>P
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<th>Component</th>
<td>Static Analyzer
</td>
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<th>Assignee</th>
<td>kremenek@apple.com
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<th>Reporter</th>
<td>mark.rogers@powermapper.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Would be very useful to warn about malloc/realloc overflows. Code like the
following is a fairly common source of exploits, because an attacker can trick
malloc into allocating less memory than the code expects, and overwrite memory
outside the malloc'd block with a payload:
wchar_t* MallocOverflow( const PdfStringTest & rString )
{
size_t lLen = rString.GetCharacterLength();
if( !lLen )
return NULL;
// should warn about size_t overflow:
// if lLen == 1GB, and sizeof(wchar_t)=4,
// then malloc'd buffer is 4 bytes long on 32-bit system
wchar_t* pDest = static_cast<wchar_t*>(malloc( sizeof(wchar_t) * (lLen + 1)
));
return pDest;
}
Any multiplication involving size_t is suspect since you sometimes see code
like this:
size_t buffLen = sizeof(wchar_t) * (lLen + 1);
wchar_t* pDest = static_cast<wchar_t*>(malloc(buffLen));
Best Regards
Mark</pre>
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