linux-kernel - [PATCH] Fix ZERO_OR_NULL_PTR(ZERO_SIZE

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Date:	Fri, 20 Jul 2007 12:13:20 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	Pekka J Enberg <penberg@...helsinki.fi>,
	torvalds@...ux-foundation.org
Cc:	Andi Kleen <ak@...e.de>, Christoph Lameter <clameter@....com>,
	linux-kernel@...r.kernel.org,
	"Michael S. Tsirkin" <mst@....mellanox.co.il>
Subject: [PATCH] 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@...co.com>
---
I finally had time to reproduce Michael's crash and debug it.  Linus's
patch is part of the story -- it doesn't help unless ZERO_OR_NULL_PTR()
is true.  With this change the crash goes away, and it seems pretty
obviously correct to me (unless I'm seriously confused).

 include/linux/slab.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

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 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)
 
 /*
-
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