patch for CVE-2012-2110 - incorrect?

[jsmith6134]

I was examining the patch for security fix for 5.0:

http://ftp.openbsd.org/pub/OpenBSD/p...ibcrypto.patch

part of the patch looks incorrect:

- if (!BUF_MEM_grow_clean(b,len+want))
+ if (len + want < len || !BUF_MEM_grow_clean(b,len+want))

"len + want < len" should always be false unless "want" can be negative. If "want" could be negative and that is what the author was trying to detect, then the code should be written:

+ if (want < 0 || !BUF_MEM_grow_clean(b,len+want))

I realize the patch does not show the full source for the file. Am I missing something?