[MERGE chakra-core#118] Fix max length condition + prevent assert crash

Yongqu · Yongqu · commit 43762284e539 · 2016-01-24T10:01:51.000-08:00
Merge pull request chakra-core#118 from obastemur:fix_assert_uintmax 1 - `UINT_MAX/3 < MAXLONG` 2 - x86/? max `size_t` == UINT_MAX Current `if` statement wouldn’t work for x86/? arch. Perhaps it wasn’t an issue thanks to following `assert`. So, success of `if` statement prevents the necessity for following `Assert`. As a result, application would throw instead of `assert` crash.
diff --git a/lib/jsrt/JsrtSourceHolder.cpp b/lib/jsrt/JsrtSourceHolder.cpp
@@ -33,8 +33,10 @@ namespace Js
             Js::JavascriptError::ThrowOutOfMemoryError(nullptr);
         }
 
-        size_t cbUtf8Buffer = (length + 1) * 3;
-        if (cbUtf8Buffer > UINT_MAX)
+        // `length` should not be bigger than MAXLONG 
+        // UINT_MAX / 3 < MAXLONG
+        size_t cbUtf8Buffer = ((UINT_MAX / 3) - 1 > length) ? (length + 1) * 3 : UINT_MAX;
+        if (cbUtf8Buffer >= UINT_MAX)
         {
             Js::JavascriptError::ThrowOutOfMemoryError(nullptr);
         }
@@ -49,7 +51,6 @@ namespace Js
             *utf8Script = HeapNewArray(utf8char_t, cbUtf8Buffer);
         }
 
-        Assert(length < MAXLONG);
         *utf8Length = utf8::EncodeIntoAndNullTerminate(*utf8Script, script, static_cast<charcount_t>(length));
         *scriptLength = length;
 

Original file line number	Diff line number	Diff line change
`@@ -33,8 +33,10 @@ namespace Js`
`33`	`33`	`Js::JavascriptError::ThrowOutOfMemoryError(nullptr);`
`34`	`34`	`}`
`35`	`35`
`36`		`- size_t cbUtf8Buffer = (length + 1) * 3;`
`37`		`- if (cbUtf8Buffer > UINT_MAX)`
	`36`	+ // `length` should not be bigger than MAXLONG
	`37`	`+ // UINT_MAX / 3 < MAXLONG`
	`38`	`+ size_t cbUtf8Buffer = ((UINT_MAX / 3) - 1 > length) ? (length + 1) * 3 : UINT_MAX;`
	`39`	`+ if (cbUtf8Buffer >= UINT_MAX)`
`38`	`40`	`{`
`39`	`41`	`Js::JavascriptError::ThrowOutOfMemoryError(nullptr);`
`40`	`42`	`}`
`@@ -49,7 +51,6 @@ namespace Js`
`49`	`51`	`*utf8Script = HeapNewArray(utf8char_t, cbUtf8Buffer);`
`50`	`52`	`}`
`51`	`53`
`52`		`- Assert(length < MAXLONG);`
`53`	`54`	`utf8Length = utf8::EncodeIntoAndNullTerminate(utf8Script, script, static_cast<charcount_t>(length));`
`54`	`55`	`*scriptLength = length;`
`55`	`56`