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From: Vlastimil Babka <vbabka@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>,
	Xishi Qiu <qiuxishi@huawei.com>
Cc: Joonsoo Kim <js1304@gmail.com>,
	David Rientjes <rientjes@google.com>,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	Laura Abbott <lauraa@codeaurora.org>,
	zhuhui@xiaomi.com, wangxq10@lzu.edu.cn,
	Linux MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: fix invalid node in alloc_migrate_target()
Date: Thu, 31 Mar 2016 15:13:41 +0200	[thread overview]
Message-ID: <56FD2285.4080600@suse.cz> (raw)
In-Reply-To: <56FA7DC8.4000902@suse.cz>

On 03/29/2016 03:06 PM, Vlastimil Babka wrote:
> On 03/25/2016 08:22 PM, Andrew Morton wrote:
>> Also, mm/mempolicy.c:offset_il_node() worries me:
>>
>> 	do {
>> 		nid = next_node(nid, pol->v.nodes);
>> 		c++;
>> 	} while (c <= target);
>>
>> Can't `nid' hit MAX_NUMNODES?
>
> AFAICS it can. interleave_nid() uses this and the nid is then used e.g.
> in node_zonelist() where it's used for NODE_DATA(nid). That's quite
> scary. It also predates git. Why don't we see crashes or KASAN finding this?

Ah, I see. In offset_il_node(), nid is initialized to -1, and the number 
of do-while iterations calling next_node() is up to the number of bits 
set in the pol->v.nodes bitmap, so it can't reach past the last set bit 
and return MAX_NUMNODES.

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  reply	other threads:[~2016-03-31 13:13 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-25  6:56 [PATCH] mm: fix invalid node in alloc_migrate_target() Xishi Qiu
2016-03-25 19:22 ` Andrew Morton
2016-03-26  5:31   ` Xishi Qiu
2016-03-29  9:52     ` Vlastimil Babka
2016-03-29 10:06       ` Vlastimil Babka
2016-03-29 10:37       ` Xishi Qiu
2016-03-29 12:21         ` Vlastimil Babka
2016-03-29 13:06   ` Vlastimil Babka
2016-03-31 13:13     ` Vlastimil Babka [this message]
2016-03-31 21:01       ` Andrew Morton
2016-04-01  8:42         ` Vlastimil Babka
2016-03-29 15:52   ` Michal Hocko
2016-03-29 12:25 ` Vlastimil Babka
2016-03-30  1:13   ` Naoya Horiguchi

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