Messages in this thread | | | Date | Fri, 1 Jun 2007 12:47:57 -0700 | From | Paul Jackson <> | Subject | Re: [RFC] [PATCH] cpuset operations causes Badness at mm/slab.c:777 warning |
| |
> 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 <pj@sgi.com> 1.925.600.0401 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |