Changeset 186643 in webkit

Timestamp:

Jul 9, 2015 3:58:05 PM (9 years ago)

Author:

mark.lam@apple.com

Message:

SymbolTable::entryFor() should do a bounds check before indexing into the localToEntry vector.
​https://bugs.webkit.org/show_bug.cgi?id=146807

Reviewed by Filip Pizlo.

When we capture an argument by name and we use "arguments", we put all of the
arguments into the scope. But destructured arguments are put into the scope
anonymously i.e. the SymbolTable knows that the scope offset is in use via
SymbolTable::m_maxScopeOffset, but that ScopeOffset won't appear in
SymbolTable::m_map.

The SymbolTable's m_localToEntry vector is synthesized from its m_map, and will
have a size which is based on the largest ScopeOffset in the m_map. If we have a
scenario where the anonymous argument is at a higher ScopeOffset than all the
named arguments, then the m_localsToEntry vector will not have an entry for it
i.e. the m_localsToEntry vector will have a size that is <= the ScopeOffset of
the anonymous argument.

Hence, SymbolTable::entryFor() should ensure that the requested ScopeOffset is
within the bounds of the m_localToEntry vector before indexing into it.

• runtime/SymbolTable.cpp:

(JSC::SymbolTable::entryFor):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• runtime/SymbolTable.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2015-07-09  Mark Lam  <mark.lam@apple.com>
+
+        SymbolTable::entryFor() should do a bounds check before indexing into the localToEntry vector.
+        https://bugs.webkit.org/show_bug.cgi?id=146807
+
+        Reviewed by Filip Pizlo.
+
+        When we capture an argument by name and we use "arguments", we put all of the
+        arguments into the scope.  But destructured arguments are put into the scope
+        anonymously i.e. the SymbolTable knows that the scope offset is in use via
+        SymbolTable::m_maxScopeOffset, but that ScopeOffset won't appear in
+        SymbolTable::m_map.
+
+        The SymbolTable's m_localToEntry vector is synthesized from its m_map, and will
+        have a size which is based on the largest ScopeOffset in the m_map.  If we have a
+        scenario where the anonymous argument is at a higher ScopeOffset than all the
+        named arguments, then the m_localsToEntry vector will not have an entry for it
+        i.e. the m_localsToEntry vector will have a size that is <= the ScopeOffset of
+        the anonymous argument.
+
+        Hence, SymbolTable::entryFor() should ensure that the requested ScopeOffset is
+        within the bounds of the m_localToEntry vector before indexing into it.
+
+        * runtime/SymbolTable.cpp:
+        (JSC::SymbolTable::entryFor):
+
 2015-07-09  Michael Saboff  <msaboff@apple.com>
 

trunk/Source/JavaScriptCore/runtime/SymbolTable.cpp

@@ -131 +131 @@
 SymbolTableEntry* SymbolTable::entryFor(const ConcurrentJITLocker& locker, ScopeOffset offset)
 {
-    return localToEntry(locker)[offset.offset()];
+    auto& toEntryVector = localToEntry(locker);
+    if (offset.offset() >= toEntryVector.size())
+        return nullptr;
+    return toEntryVector[offset.offset()];
 }