Re: [PATCH] exec: do not leave bprm->interp on stack

P J P wrote:

  Hello Kees,

+-- On Wed, 24 Oct 2012, Kees Cook wrote --+
| What should the code here _actually_ be doing? The _script and _misc 
| handlers expect to rewrite the bprm contents and recurse, but the module 
| loader want to try again. It's not clear to me what the binfmt module 
| handler is even there for; I don't see any binfmt-XXXX aliases in the tree. 
| If nothing uses it, should we just rip it out? That would solve it too.

I've been following this issue and updated versions of HDs patch. Below is a 
small patch to search_binary_handler() routine, which attempts to make the 
request_module call before calling load_script routine.

Besides fixing the stack disclosure issue it also helps to *simplify* the 
search_binary_handler routine by removing the -for (try=0;try<2;try++)- loop.

I'd really appreciate any comments/suggestions you may have.

Excuse me, but why do you change definition of printable(c) ?
Looks like a regression.

Wouldn't your patch trigger call request_module() whenever a script
starting with "#!/bin/sh" is executed? 

And if you meant

if (!(printable(bprm->buf[0]) && printable(bprm->buf[1])
	&& printable(bprm->buf[2]) && printable(bprm->buf[3])))

then, wouldn't that trigger request_module() recursion?