Re: [PATCH net V3 2/2] ptr_ring: fail on large queue size (>64K)

On 2018年02月09日 03:09, David Miller wrote:

From: Jason Wang <redacted>
Date: Thu,  8 Feb 2018 11:59:25 +0800

quoted

We need limit the maximum size of queue, otherwise it may cause
several side effects e.g slab will warn when the size exceeds
KMALLOC_MAX_SIZE. Using KMALLOC_MAX_SIZE still looks too so this patch
tries to limit it to 64K. This value could be revisited if we found a
real case that needs more.

Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com
Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")
Signed-off-by: Jason Wang <redacted>

  ...

quoted

@@ -466,6 +468,8 @@ 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 > PTR_RING_MAX_ALLOC)
+		return NULL;
  	return kvmalloc_array(size, sizeof(void *), gfp | __GFP_ZERO);
  }

This doesn't limit the allocation to 64K.  It limits it to 64K * sizeof(void *).

Right, will fix this.

Thanks