linux-kernel - Re: [PATCH] kmemleak: Never return a pointer you didn't 'get'

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Message-ID: <1303896680.15101.1.camel@e102109-lin.cambridge.arm.com>
Date:	Wed, 27 Apr 2011 10:31:20 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Phil Carmody <ext-phil.2.carmody@...ia.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kmemleak: Never return a pointer you didn't 'get'

On Thu, 2011-04-21 at 12:39 +0100, Phil Carmody wrote:
> Old - If you don't get the last pointer that you looked at, then it will
> still be put, as there's no way of knowing you didn't get it.
> 
> New - If you didn't get it, then it refers to something deleted, and
> your work is done, so return NULL.
> 
> Signed-off-by: Phil Carmody <ext-phil.2.carmody@...ia.com>

Good catch. But I think the code may look slightly simpler as below:

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index c1d5867..aacee45 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1414,9 +1414,12 @@ static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 	++(*pos);
 
 	list_for_each_continue_rcu(n, &object_list) {
-		next_obj = list_entry(n, struct kmemleak_object, object_list);
-		if (get_object(next_obj))
+		struct kmemleak_object *obj =
+			list_entry(n, struct kmemleak_object, object_list);
+		if (get_object(obj)) {
+			next_obj = obj;
 			break;
+		}
 	}
 
 	put_object(prev_obj);


Thanks.

-- 
Catalin


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