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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - libprofile: allocateOneNode() can overflow CurrentVNode"
href="https://llvm.org/bugs/show_bug.cgi?id=27882">27882</a>
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<th>Summary</th>
<td>libprofile: allocateOneNode() can overflow CurrentVNode
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<th>Product</th>
<td>compiler-rt
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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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>compiler-rt
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>vsk@apple.com
</td>
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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>In allocateOneNode(), we increment CurrentVNode without first checking if it's
greater than EndVnode. This could eventually cause CurrentVNode to overflow and
return a bad vnode:
106 Node = COMPILER_RT_PTR_FETCH_ADD(ValueProfNode, CurrentVNode, 1);
107 if (Node >= EndVNode) {
108 if (OutOfNodesWarnings++ < MAX_VP_WARNS) {
109 PROF_WARN("Unable to track new values: %s. "
110 " Consider using option -mllvm -vp-counters-per-site=<n> to
allocate more"
111 " value profile counters at compile time. \n",
112 "Running out of static counters");
113 }
114 return 0;
115 }
116 return Node;
Sean suggested limiting increments of CurrentVNode to #threads past EndVNode.
Another option is to attempt to CmpExchange CurrentVnode to its next value
while (CurrentVNode + 1 < EndVNode). We'd return if the CmpExchange succeeds.
If the loop exits we'd return NULL.</pre>
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