[PATCH] git-fast-import possible memory corruption problem

Hello.
While trying to convert NetBSD CVS repository to Git, I've been
experiencing 100% reproducible crash of git-fast-import.  After
poking here and there and I noticed a dubious code fragment in
pool_alloc():
	:

        r = p->next_free;
        /* round out to a 'uintmax_t' alignment */
        if (len & (sizeof(uintmax_t) - 1))
                len += sizeof(uintmax_t) - (len & (sizeof(uintmax_t) - 1));
        p->next_free += len;
        return r;

As the `round out' takes place AFTER it found the room in the mem_pool,
there's a small chance of p->next_free being set outside of the chosen
area, up to (sizeof(uintmax_t) - 1) bytes.  pool_strdup() is one of the
functions which can trigger the problem, when pool_alloc() finds a room
at the end of a pool entry and the requested length is not multiple of
size(uintmax_t).  I believe attached patch addresses this problem.

Best regards,
YONETANI Tomokazu.