From: 王擎 <wangqing@vivo.com>
To: Muchun Song <songmuchun@bytedance.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re:Re: [Phishing Risk] [External] [PATCH] mm: add GFP_ATOMIC flag after local_lock_irqsave
Date: Tue, 6 Jul 2021 10:41:21 +0800 (GMT+08:00) [thread overview]
Message-ID: <AEsAOwC*DyQcdDctDg-oWKqc.3.1625539281909.Hmail.wangqing@vivo.com> (raw)
In-Reply-To: <CAMZfGtUbX+TAx-7RJ4ZpoNLHDa9mp6k+DBqHaYiLjhSJokh3Sw@mail.gmail.com>
>On Mon, Jul 5, 2021 at 9:57 PM Wang Qing <wangqing@vivo.com> wrote:
>>
>> Use GFP_ATOMIC when local_lock_irqsave in __alloc_pages_bulk
>>
>> Reported-by: syzbot+e45919db2eab5e837646@syzkaller.appspotmail.com
>> Signed-off-by: Wang Qing <wangqing@vivo.com>
>> ---
>> mm/page_alloc.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index d6e94cc..3016ba5
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5309,7 +5309,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
>> }
>> nr_account++;
>>
>> - prep_new_page(page, 0, gfp, 0);
>> + prep_new_page(page, 0, gfp | GFP_ATOMIC, 0);
>
>Hi Wang Qing,
>
>I didn't get the point here. IIUC, prep_new_page() will not allocate
>memory. So why do we need GFP_ATOMIC? What I missed here?
>
>Thanks.
prep_new_page() will allocate memory in some scenarios. For details,
you can check the bugs detected by syzkaller:
https://syzkaller.appspot.com/bug?id=91c2030241ada0e5d21877f8f2f44c98cffc04bb
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:96
___might_sleep.cold+0x1f1/0x237 kernel/sched/core.c:9153
prepare_alloc_pages+0x3da/0x580 mm/page_alloc.c:5179
__alloc_pages+0x12f/0x500 mm/page_alloc.c:5375
alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272
stack_depot_save+0x39d/0x4e0 lib/stackdepot.c:303
save_stack+0x15e/0x1e0 mm/page_owner.c:120
__set_page_owner+0x50/0x290 mm/page_owner.c:181
prep_new_page mm/page_alloc.c:2445 [inline]
__alloc_pages_bulk+0x8b9/0x1870 mm/page_alloc.c:5313
Thanks.
Qing
>
>> if (page_list)
>> list_add(&page->lru, page_list);
>> else
>> --
>> 2.7.4
>>
next prev parent reply other threads:[~2021-07-06 2:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-05 13:57 [PATCH] mm: add GFP_ATOMIC flag after local_lock_irqsave Wang Qing
2021-07-06 2:32 ` [Phishing Risk] [External] " Muchun Song
2021-07-06 2:32 ` Muchun Song
2021-07-06 2:41 ` 王擎 [this message]
2021-07-06 2:41 ` 王擎
2021-07-06 3:05 ` Muchun Song
2021-07-06 3:05 ` Muchun Song
2021-07-06 3:13 ` 王擎
2021-07-06 3:13 ` 王擎
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