2021-07-05 13:59:18

by 王擎

Subject: [PATCH] mm: add GFP_ATOMIC flag after local_lock_irqsave

Use GFP_ATOMIC when local_lock_irqsave in __alloc_pages_bulk

Reported-by: [email protected]
Signed-off-by: Wang Qing <[email protected]>
---
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);
if (page_list)
list_add(&page->lru, page_list);
else
--
2.7.4

2021-07-06 02:34:18

by Muchun Song

Subject: Re: [Phishing Risk] [External] [PATCH] mm: add GFP_ATOMIC flag after local_lock_irqsave

On Mon, Jul 5, 2021 at 9:57 PM Wang Qing <[email protected]> wrote:
>
> Use GFP_ATOMIC when local_lock_irqsave in __alloc_pages_bulk
>
> Reported-by: [email protected]
> Signed-off-by: Wang Qing <[email protected]>
> ---
> 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.

> if (page_list)
> list_add(&page->lru, page_list);
> else
> --
> 2.7.4
>

2021-07-06 02:50:48

by 王擎

Subject: Re:Re: [Phishing Risk] [External] [PATCH] mm: add GFP_ATOMIC flag after local_lock_irqsave

>On Mon, Jul 5, 2021 at 9:57 PM Wang Qing <[email protected]> wrote:
>>
>> Use GFP_ATOMIC when local_lock_irqsave in __alloc_pages_bulk
>>
>> Reported-by: [email protected]
>> Signed-off-by: Wang Qing <[email protected]>
>> ---
>> 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
>>

2021-07-06 03:09:11

by Muchun Song

Subject: Re: Re: [Phishing Risk] [External] [PATCH] mm: add GFP_ATOMIC flag after local_lock_irqsave

On Tue, Jul 6, 2021 at 10:41 AM 王擎 <[email protected]> wrote:
>
>
> >On Mon, Jul 5, 2021 at 9:57 PM Wang Qing <[email protected]> wrote:
> >>
> >> Use GFP_ATOMIC when local_lock_irqsave in __alloc_pages_bulk
> >>
> >> Reported-by: [email protected]
> >> Signed-off-by: Wang Qing <[email protected]>
> >> ---
> >> 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

Got it. But I don't think the fix you mentioned above was
appropriate. What if GFP_KERNEL | GFP_ATOMIC?

Thanks.

>
> Thanks.
>
> Qing
>
> >
> >> if (page_list)
> >> list_add(&page->lru, page_list);
> >> else
> >> --
> >> 2.7.4
> >>
>
>

2021-07-06 03:16:48

by 王擎

Subject: Re:Re: Re: [Phishing Risk] [External] [PATCH] mm: add GFP_ATOMIC flag after local_lock_irqsave

>On Tue, Jul 6, 2021 at 10:41 AM 王擎 <[email protected]> wrote:
>>
>>
>> >On Mon, Jul 5, 2021 at 9:57 PM Wang Qing <[email protected]> wrote:
>> >>
>> >> Use GFP_ATOMIC when local_lock_irqsave in __alloc_pages_bulk
>> >>
>> >> Reported-by: [email protected]
>> >> Signed-off-by: Wang Qing <[email protected]>
>> >> ---
>> >> 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
>
>Got it. But I don't think the fix you mentioned above was
>appropriate. What if GFP_KERNEL | GFP_ATOMIC?

Yes agree, but I haven't figured out what will happen this way,
the test has been passed in syzkaller.
Or how about gfp | GFP_ATOMIC & ~GFP_KERNEL ?

Thanks,

Qing
>
>Thanks.
>
>>
>> Thanks.
>>
>> Qing
>>
>> >
>> >> if (page_list)
>> >> list_add(&page->lru, page_list);
>> >> else
>> >> --
>> >> 2.7.4
>> >>
>>
>>