Re: [RFC][PATCH] mm: Remove ZERO_SIZE_PTR.

[Tetsuo Handa]

Christoph Lameter wrote:
> On Fri, 26 Feb 2010, Tetsuo Handa wrote:
> 
> > Everybody should check for ptr != NULL, and most callers are actually checking
> > for ptr != NULL. But nobody is checking for ptr != ZERO_SIZE_PTR.
> 
> That is so intentionally because some kernel subsystem can do a zero size
> allocation.
> 
So, not only users *can* do zero size allocation,
but also there *are* users who are intentionally doing zero size allocation.
Then, we can't remove ZERO_SIZE_PTR.

> > Yes, this is the fault of caller. But ZERO_SIZE_PTR is too small value to
> > distinguish "NULL pointer dereference" and "ZERO_SIZE_PTR dereference" because
> > address printed by oops message can easily exceed ZERO_SIZE_PTR when
> > "struct foo" is large.
> 
> Correct.

Maybe PAGE_SIZE / 2 is better than 16?

Thanks.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/