[cfe-dev] clang feature request: integer overflow check in operator new

[Daniel Dunbar]

Hi Felix,

Please file a bugzilla for this specic issue, it certainly sounds like
a reasonable addition.

 - Daniel

On Tue, Mar 23, 2010 at 8:17 AM, Felix von Leitner <felix-llvm at fefe.de> wrote:
> Dear clang developers,
>
> I have a humble feature request for clang, now that it officially
> supports C++: integer overflow check in operator new.
>
> Basically, in code like this:
>
>   int* foo=new int[somevalue];
>
> the compiler does an implicit somevalue*sizeof(int) and passes that
> value to operator new.  If that multiplication overflows, this is a
> security vulnerability.  The Microsoft solution is to use the overflow
> flag on x86 to set the resulting value to (size_t)-1, which will then
> make operator new fail.  There are caveats to this, obviously, but it is
> an important step to make and it cannot be done without compiler help.
>
> Would it be possible to get clang to do something like this in the code
> generator?
>
> That would really help the world be a more secure place in the long run,
> and maybe it can even help convince g++ to follow suit.  Also, I really
> like how you place emphasis on good diagnostic messages in clang, and I
> will try to come up with suggestions on what to do even better there.
> My biggest hope long-term would be to provide a framework for data flow
> analysis using the link time optimization framework.  Now finally
> compilers have enough context to do that kind of analysis, it is a great
> opportunity to do some good.  I am thinking of some kind of tainting
> warning.  And it would also be very helpful if clang supported something
> like SAL<http://msdn.microsoft.com/en-us/library/ms235402(VS.80).aspx>
>
> Basically anything that allows me to annotate my library so that using
> it incorrectly triggers better warnings would be greatly appreciated.
>
> Thanks,
>
> Felix
>
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