[STABLE PATCH] slub: make ->cpu_partial unsigned int

[STABLE PATCH] slub: make ->cpu_partial unsigned int

[zhong jiang]

From: Alexey Dobriyan <adobriyan@gmail.com>

        /*
         * cpu_partial determined the maximum number of objects
         * kept in the per cpu partial lists of a processor.
         */

Can't be negative.

I hit a real issue that it will result in a large number of memory leak.
Because Freeing slabs are in interrupt context. So it can trigger this issue.
put_cpu_partial can be interrupted more than once.
due to a union struct of lru and pobjects in struct page, when other core handles
page->lru list, for eaxmple, remove_partial in freeing slab code flow, It will
result in pobjects being a negative value(0xdead0000). Therefore, a large number
of slabs will be added to per_cpu partial list.

I had posted the issue to community before. The detailed issue description is as follows.

Link: https://www.spinics.net/lists/kernel/msg2870979.html

After applying the patch, The issue is fixed. So the patch is a effective bugfix.
It should go into stable.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: stable@vger.kernel.org 
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
---
 include/linux/slub_def.h | 3 ++-
 mm/slub.c                | 6 +++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 3388511..9b681f2 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -67,7 +67,8 @@ struct kmem_cache {
 	int size;		/* The size of an object including meta data */
 	int object_size;	/* The size of an object without meta data */
 	int offset;		/* Free pointer offset. */
-	int cpu_partial;	/* Number of per cpu partial objects to keep around */
+	/* Number of per cpu partial objects to keep around */
+	unsigned int cpu_partial;
 	struct kmem_cache_order_objects oo;
 
 	/* Allocation and freeing of slabs */
diff --git a/mm/slub.c b/mm/slub.c
index 2284c43..c33b0e1 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1661,7 +1661,7 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
 {
 	struct page *page, *page2;
 	void *object = NULL;
-	int available = 0;
+	unsigned int available = 0;
 	int objects;
 
 	/*
@@ -4674,10 +4674,10 @@ static ssize_t cpu_partial_show(struct kmem_cache *s, char *buf)
 static ssize_t cpu_partial_store(struct kmem_cache *s, const char *buf,
 				 size_t length)
 {
-	unsigned long objects;
+	unsigned int objects;
 	int err;
 
-	err = kstrtoul(buf, 10, &objects);
+	err = kstrtouint(buf, 10, &objects);
 	if (err)
 		return err;
 	if (objects && !kmem_cache_has_cpu_partial(s))
-- 
1.7.12.4

Re: [STABLE PATCH] slub: make ->cpu_partial unsigned int

[Christopher Lameter]

On Thu, 27 Sep 2018, zhong jiang wrote:

> From: Alexey Dobriyan <adobriyan@gmail.com>
>
>         /*
>          * cpu_partial determined the maximum number of objects
>          * kept in the per cpu partial lists of a processor.
>          */
>
> Can't be negative.

True.

> I hit a real issue that it will result in a large number of memory leak.
> Because Freeing slabs are in interrupt context. So it can trigger this issue.
> put_cpu_partial can be interrupted more than once.
> due to a union struct of lru and pobjects in struct page, when other core handles
> page->lru list, for eaxmple, remove_partial in freeing slab code flow, It will
> result in pobjects being a negative value(0xdead0000). Therefore, a large number
> of slabs will be added to per_cpu partial list.

That sounds like it needs more investigation. Concurrent use of page
fields for other purposes can cause serious bugs.

>
> I had posted the issue to community before. The detailed issue description is as follows.

I did not see it. Please make sure to CC the maintainers.

Re: [STABLE PATCH] slub: make ->cpu_partial unsigned int

[Greg KH]

On Thu, Sep 27, 2018 at 10:43:40PM +0800, zhong jiang wrote:
> From: Alexey Dobriyan <adobriyan@gmail.com>
> 
>         /*
>          * cpu_partial determined the maximum number of objects
>          * kept in the per cpu partial lists of a processor.
>          */
> 
> Can't be negative.
> 
> I hit a real issue that it will result in a large number of memory leak.
> Because Freeing slabs are in interrupt context. So it can trigger this issue.
> put_cpu_partial can be interrupted more than once.
> due to a union struct of lru and pobjects in struct page, when other core handles
> page->lru list, for eaxmple, remove_partial in freeing slab code flow, It will
> result in pobjects being a negative value(0xdead0000). Therefore, a large number
> of slabs will be added to per_cpu partial list.
> 
> I had posted the issue to community before. The detailed issue description is as follows.
> 
> Link: https://www.spinics.net/lists/kernel/msg2870979.html
> 
> After applying the patch, The issue is fixed. So the patch is a effective bugfix.
> It should go into stable.

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

Re: [STABLE PATCH] slub: make ->cpu_partial unsigned int

[zhong jiang]

On 2018/9/27 23:46, Greg KH wrote:
> On Thu, Sep 27, 2018 at 10:43:40PM +0800, zhong jiang wrote:
>> From: Alexey Dobriyan <adobriyan@gmail.com>
>>
>>         /*
>>          * cpu_partial determined the maximum number of objects
>>          * kept in the per cpu partial lists of a processor.
>>          */
>>
>> Can't be negative.
>>
>> I hit a real issue that it will result in a large number of memory leak.
>> Because Freeing slabs are in interrupt context. So it can trigger this issue.
>> put_cpu_partial can be interrupted more than once.
>> due to a union struct of lru and pobjects in struct page, when other core handles
>> page->lru list, for eaxmple, remove_partial in freeing slab code flow, It will
>> result in pobjects being a negative value(0xdead0000). Therefore, a large number
>> of slabs will be added to per_cpu partial list.
>>
>> I had posted the issue to community before. The detailed issue description is as follows.
>>
>> Link: https://www.spinics.net/lists/kernel/msg2870979.html
>>
>> After applying the patch, The issue is fixed. So the patch is a effective bugfix.
>> It should go into stable.
> <formletter>
>
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree.  Please read:
>     https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> for how to do this properly.
>
> </formletter>
Will resend with proper format.

Thanks,
zhong jiang