> The allocated array has 0 bytes. Any dereference is an error.
Well, then, that doesn't work either.
We -agree- we can't have this failing. You suggested (if I understood
correctly, which I doubt) that we set the pointer to NULL, and noted
that derefencing a NULL pointer would fail. I agree such derefences
would fail, and tried to point out that this would be bad. We can't
have pointer dereferences failing in the kernel ... duh.
Your reply seems like a non sequiter to me, pointing out that having
a pointer to an array of 0 bytes fails as well. Ok - that's bad too.
So we cannot have a NULL pointer, used unchecked, and we cannot have
a non-NULL pointer to a zero byte array, used unchecked.
As I said, and as I thought Srinivasa coded, with these patch lines:
@@ -1772,6 +1779,9 @@ static ssize_t cpuset_tasks_read(struct
{
struct ctr_struct *ctr = file->private_data;
+ if (!ctr->buf) /* No tasks in this cpuset */
+ return 0;
+
return simple_read_from_buffer(buf, nbytes, ppos, ctr->buf, ctr->bufsz);
}
we actually have to check the NULL-ness (or emptiness) of this thing,
down where it would be used, to avoid using NULL or empty things.
Summary - Srinivasa's patch still looks ok to me. This followup
discussion between you and I is just confusing me - sorry.
--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <[email protected]> 1.925.600.0401
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