[PATCH net] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[PATCH net] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[Jason Wang]

To avoid slab to warn about exceeded size, fail early if queue
occupies more than KMALLOC_MAX_SIZE.

Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 include/linux/ptr_ring.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index 1883d61..4b862da 100644
--- a/include/linux/ptr_ring.h
+++ b/include/linux/ptr_ring.h
@@ -466,6 +466,8 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
 
 static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
 {
+	if (size > KMALLOC_MAX_SIZE)
+		return NULL;
 	return kcalloc(size, sizeof(void *), gfp);
 }
 
-- 
2.7.4

Re: [PATCH net] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[Jason Wang]

On 2018年02月07日 16:08, Jason Wang wrote:
> To avoid slab to warn about exceeded size, fail early if queue
> occupies more than KMALLOC_MAX_SIZE.
>
> Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>   include/linux/ptr_ring.h | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> index 1883d61..4b862da 100644
> --- a/include/linux/ptr_ring.h
> +++ b/include/linux/ptr_ring.h
> @@ -466,6 +466,8 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
>   
>   static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
>   {
> +	if (size > KMALLOC_MAX_SIZE)
> +		return NULL;
>   	return kcalloc(size, sizeof(void *), gfp);
>   }
>   

Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")

Re: [PATCH net] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[Michael S. Tsirkin]

On Wed, Feb 07, 2018 at 05:17:59PM +0800, Jason Wang wrote:
> 
> 
> On 2018年02月07日 16:08, Jason Wang wrote:
> > To avoid slab to warn about exceeded size, fail early if queue
> > occupies more than KMALLOC_MAX_SIZE.
> > 
> > Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > ---
> >   include/linux/ptr_ring.h | 2 ++
> >   1 file changed, 2 insertions(+)
> > 
> > diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> > index 1883d61..4b862da 100644
> > --- a/include/linux/ptr_ring.h
> > +++ b/include/linux/ptr_ring.h
> > @@ -466,6 +466,8 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
> >   static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
> >   {
> > +	if (size > KMALLOC_MAX_SIZE)
> > +		return NULL;
> >   	return kcalloc(size, sizeof(void *), gfp);
> >   }
> 
> Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")

That's probably not enough. How about switching to kvmalloc and limiting
this drastically to e.g. 64K. I vaguely remember that some wise man said
that should be enough for everybody :)

-- 
MST

Re: [PATCH net] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[Jason Wang]

On 2018年02月07日 23:15, Michael S. Tsirkin wrote:
> On Wed, Feb 07, 2018 at 05:17:59PM +0800, Jason Wang wrote:
>>
>> On 2018年02月07日 16:08, Jason Wang wrote:
>>> To avoid slab to warn about exceeded size, fail early if queue
>>> occupies more than KMALLOC_MAX_SIZE.
>>>
>>> Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com
>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>> ---
>>>    include/linux/ptr_ring.h | 2 ++
>>>    1 file changed, 2 insertions(+)
>>>
>>> diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
>>> index 1883d61..4b862da 100644
>>> --- a/include/linux/ptr_ring.h
>>> +++ b/include/linux/ptr_ring.h
>>> @@ -466,6 +466,8 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
>>>    static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
>>>    {
>>> +	if (size > KMALLOC_MAX_SIZE)
>>> +		return NULL;
>>>    	return kcalloc(size, sizeof(void *), gfp);
>>>    }
>> Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")
> That's probably not enough. How about switching to kvmalloc and limiting
> this drastically to e.g. 64K. I vaguely remember that some wise man said
> that should be enough for everybody :)
>

Okay, let me post a V2 to see if there's any objection.

Thanks

Re: [PATCH net] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[Michael S. Tsirkin]

On Wed, Feb 07, 2018 at 04:08:25PM +0800, Jason Wang wrote:
> To avoid slab to warn about exceeded size, fail early if queue
> occupies more than KMALLOC_MAX_SIZE.
> 
> Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  include/linux/ptr_ring.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> index 1883d61..4b862da 100644
> --- a/include/linux/ptr_ring.h
> +++ b/include/linux/ptr_ring.h
> @@ -466,6 +466,8 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
>  
>  static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
>  {
> +	if (size > KMALLOC_MAX_SIZE)
> +		return NULL;
>  	return kcalloc(size, sizeof(void *), gfp);
>  }

I guess this approach does begin to make more sense
at least as a temporary stop-gap.

But does this actually prevent the crash in all cases?

size is in void* entry units, KMALLOC_MAX_SIZE is in bytes.


>  
> -- 
> 2.7.4