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+e4d4f9ddd42955397...@syzkaller.appspotmail.com
Signed-off-by: Jason Wang <jasow...@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