linux-kernel - Re: [PATCH 1/9] mm: kmemleak: properly disable task stack scanning

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Message-ID: <Y9FA+fFBytksYZi9@arm.com>
Date:   Wed, 25 Jan 2023 14:47:21 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     George Prekas <george@...abrica.net>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Andrei Vagin <avagin@...il.com>
Subject: Re: [PATCH 1/9] mm: kmemleak: properly disable task stack scanning

On Mon, Jan 23, 2023 at 11:04:11AM -0600, George Prekas wrote:
> @@ -1586,23 +1608,6 @@ static void kmemleak_scan(void)
>  	}
>  	put_online_mems();
>  
> -	/*
> -	 * Scanning the task stacks (may introduce false negatives).
> -	 */
> -	if (kmemleak_stack_scan) {
> -		struct task_struct *p, *g;
> -
> -		rcu_read_lock();
> -		for_each_process_thread(g, p) {
> -			void *stack = try_get_task_stack(p);
> -			if (stack) {
> -				scan_block(stack, stack + THREAD_SIZE, NULL);
> -				put_task_stack(p);
> -			}
> -		}
> -		rcu_read_unlock();
> -	}

On architectures without VMAP_STACK, we still need the above otherwise
it could lead to some false positives.

-- 
Catalin