Re: [PATCH V4 1/2] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[Jason Wang]

On 2018年02月11日 03:32, Eric Biggers wrote:

Hi Jason,

On Fri, Feb 09, 2018 at 05:45:49PM +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+e4d4f9ddd42955397...@syzkaller.appspotmail.com
Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")
Signed-off-by: Jason Wang 
---
  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..6051a5f 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 * sizeof(void *) > KMALLOC_MAX_SIZE)
+   return NULL;

Are you sure that size can't be over 0x4000?  The proper way to write this
(safe from integer overflow) would be:

if (size > KMALLOC_MAX_SIZE / sizeof(void *))
return NULL;

- Eric


Good catch.

Will post a fix.

Thanks

Re: [PATCH V4 1/2] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[Eric Biggers]

Hi Jason,

On Fri, Feb 09, 2018 at 05:45:49PM +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+e4d4f9ddd42955397...@syzkaller.appspotmail.com
> Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")
> Signed-off-by: Jason Wang 
> ---
>  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..6051a5f 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 * sizeof(void *) > KMALLOC_MAX_SIZE)
> + return NULL;

Are you sure that size can't be over 0x4000?  The proper way to write this
(safe from integer overflow) would be:

if (size > KMALLOC_MAX_SIZE / sizeof(void *))
return NULL;

- Eric

Re: [PATCH V4 1/2] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[David Miller]

From: Jason Wang 
Date: Fri,  9 Feb 2018 17:45:49 +0800

> To avoid slab to warn about exceeded size, fail early if queue
> occupies more than KMALLOC_MAX_SIZE.
> 
> Reported-by: syzbot+e4d4f9ddd42955397...@syzkaller.appspotmail.com
> Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")
> Signed-off-by: Jason Wang 

Applied.

Re: [PATCH V4 1/2] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[Michael S. Tsirkin]

On Fri, Feb 09, 2018 at 05:45:49PM +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+e4d4f9ddd42955397...@syzkaller.appspotmail.com
> Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")
> Signed-off-by: Jason Wang 

Acked-by: Michael S. Tsirkin 

> ---
>  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..6051a5f 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 * sizeof(void *) > KMALLOC_MAX_SIZE)
> + return NULL;
>   return kcalloc(size, sizeof(void *), gfp);
>  }
>  
> -- 
> 2.7.4