linux-kernel - [PATCH] slub: fix slab_pad

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Message-ID: <4A9FCDC6.3060003@gmail.com>
Date:	Thu, 03 Sep 2009 16:08:06 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
CC:	Pekka Enberg <penberg@...helsinki.fi>,
	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	Patrick McHardy <kaber@...sh.net>, Robin Holt <holt@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesper Dangaard Brouer <hawk@...x.dk>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Netfilter Developers <netfilter-devel@...r.kernel.org>,
	paulmck@...ux.vnet.ibm.com
Subject: [PATCH] slub: fix slab_pad_check()

Christoph Lameter a écrit :
> On Thu, 3 Sep 2009, Eric Dumazet wrote:
> 
>> on a SLAB_DESTROY_BY_RCU cache, there is no need to try to optimize this
>> rcu_barrier() call, unless we want superfast reboot/halt sequences...
> 
> I stilll think that the action to quiesce rcu is something that the caller
> of kmem_cache_destroy must take care of.

Do you mean :

if (kmem_cache_shrink(s) == 0) {
	rcu_barrier();
	kmem_cache_destroy_no_rcu_barrier(s);
} else {
	kmem_cache_destroy_with_rcu_barrier_because_SLAB_DESTROY_BY_RCU_cache(s);
}

What would be the point ?



> 
> Could you split this into two patches: One that addresses the poison and
> another that deals with rcu?
> 

Sure, here is the poison thing

[PATCH] slub: fix slab_pad_check()

When SLAB_POISON is used and slab_pad_check() finds an overwrite of the
slab padding, we call restore_bytes() on the whole slab, not only
on the padding.

Reported-by: Zdenek Kabelac <zdenek.kabelac@...il.com>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
diff --git a/mm/slub.c b/mm/slub.c
index b9f1491..0ac839f 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -646,7 +646,7 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page)
 	slab_err(s, page, "Padding overwritten. 0x%p-0x%p", fault, end - 1);
 	print_section("Padding", end - remainder, remainder);
 
-	restore_bytes(s, "slab padding", POISON_INUSE, start, end);
+	restore_bytes(s, "slab padding", POISON_INUSE, end - remainder, end);
 	return 0;
 }
 
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