Re: [RFC] fix slub krealloc()

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 23 Jul 2007 13:32:06 -0700
Christoph Lameter <clameter@sgi.com> wrote:

> On Wed, 18 Jul 2007 17:42:11 +0200
> Johannes Berg <johannes@sipsolutions.net> wrote:
> 
> > Commit ef2ad80c7d255ed0449eda947c2d700635b7e0f5 breaks
> > krealloc(NULL, ...) badly, it BUG_ON()s.
> > 
> > This patch fixes it but the fix should probably be in mm/util.c
> > because the documentation says that krealloc(NULL, x, gfp) is
> > equivalent to kmalloc(x, gfp) and that's not true any more even after
> > this patch when you do krealloc(NULL, 0, gfp)
> 
> Right. We need to fix util.c. ksize should not be called with a NULL
> parameter.
> Index: linux-2.6/mm/util.c
> ===================================================================
> --- linux-2.6.orig/mm/util.c	2007-07-23 13:29:42.000000000 -0700
> +++ linux-2.6/mm/util.c	2007-07-23 13:31:28.000000000 -0700
> @@ -88,7 +88,11 @@ void *krealloc(const void *p, size_t new
>  		return ZERO_SIZE_PTR;
>  	}
>  
> -	ks = ksize(p);
> +	if (p)
> +		ks = ksize(p);
> +	else
> +		ks = 0;
> +
>  	if (ks >= new_size)
>  		return (void *)p;
>  

I think we already fixed this?

commit 1d4ec7b1d6f130818f9b62dea3411d9ee2ff6ff6
Author: Roland Dreier <rdreier@cisco.com>
Date:   Fri Jul 20 12:13:20 2007 -0700

    Fix ZERO_OR_NULL_PTR(ZERO_SIZE_PTR)
    
    The comparison with ZERO_SIZE_PTR in ZERO_OR_NULL_PTR() needs to be <=
    (not just <) so that ZERO_OR_NULL_PTR(ZERO_SIZE_PTR) is 1.
    
    Signed-off-by: Roland Dreier <rolandd@cisco.com>
    [ Duh!  - Linus ]
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 7d0ecc1..d859354 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -40,7 +40,7 @@ #define SLAB_TRACE		0x00200000UL	/* Trac
  */
 #define ZERO_SIZE_PTR ((void *)16)
 
-#define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) < \
+#define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) <= \
 				(unsigned long)ZERO_SIZE_PTR)
 
 /*