Re: [PATCH] include/linux/slab.h: new KFREE() macro.

Amit Choudhary
2007-01-10T00:00:54Z

--- Valdis.Kletnieks@vt.edu wrote:

> On Tue, 09 Jan 2007 11:02:35 PST, Amit Choudhary said:
> > Correct. And doing kfree(x); x=NULL; is not hiding that. These issues can still be debugged by
> > using the slab debugging options. One other benefit of doing this is that if someone tries to
> > access the same memory again using the variable 'x', then he will get an immediate crash.

What did you understand when I wrote that "if you access the same memory again using the variable
'x"?

Using variable 'x' means using variable 'x' and not variable 'y'.

And
> the
> > problem can be solved immediately, without using the slab debugging options. I do not yet
> > understand how doing this hides the bugs, obfuscates the code, etc. because I haven't seen an
> > example yet, but only blanket statements.
>
> char *broken() {
> char *x, *y;
> x = kmalloc(100);
> y = x;
> kfree(x);
> x = NULL;
> return y;
> }
>
> Setting x to NULL doesn't do anything to fix the *real* bug here, because
> the problematic reference is held in y, not x.

Did I ever say that it fixes that kind of bug?

>So you never get a crash
> because somebody dereferences x.
>

Dereferencing 'x' means dereferencing 'x' and not dereferencing 'y'.

-Amit

__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around