Re: Re: alloca() problem
| From: | Ilia Alshanetsky | Date: | Mon, 14 Jun 2004 16:10:46 +0000 |
| Subject: | Re: Re: alloca() problem | ||
| References: | 1 2 | Groups: | php.internals |
| Request: | Send a blank email to internals+get-10443@lists.php.net to get a copy of this message | ||
Virtually all current uses involve some form of user input, which means that
the user can exploit the problem. When bar[2048] is used to create a buffer
of a certain known size that never change, with alloca a buffer of undermined
size is created in most cases.
The only 'safe' way to use the function would be to put it inside a wrapper
that would check the size against some preset limit and based on that
determine if alloca or emalloc should be used. The length would also need to
be stored to allow the free wrapper to determine if efree() is needed. These
safety checks may offset the miniscule speed advantage gained by using alloca
anyway, especially when the length is being calculated inside alloca call.
Ilia