[PATCH 2/2] ash: use alloca to get rid of setjmp

[Ron Yorston]

Rich Felker wrote:
>I suspect it can easily be made to do arbitrary code execution when
>otherwise-safe (e.g. checked against whitelist for special chars)
>strings from untrusted input are expanded inside eval commands.
>
>Any new use of VLA/alloca should be completely banned. It's basically
>always an exploitable bug.

I certainly don't want to be responsible for the next Shellshock.

Following up with a patch to revert the use of alloca.  The old code was
ugly but at least it should be safe.  I can't see any other way to do it.

I did spot an opportunity to save a few bytes, though, so there's a second
patch to partly make up for the loss of the 66 byte saving in the reverted
patch.

Ron