ptr_ring: wrap back ->producer in __ptr_ring_swap_queue()

__ptr_ring_swap_queue() tries to move pointers from the old ring to the new one, but it forgets to check if ->producer is beyond the new size at the end of the operation. This leads to an out-of-bound access in __ptr_ring_produce() as reported by syzbot. Reported-by: [email protected] Fixes: 5d49de5 ("ptr_ring: resize support") Cc: "Michael S. Tsirkin" <[email protected]> Cc: John Fastabend <[email protected]> Cc: Jason Wang <[email protected]> Signed-off-by: Cong Wang <[email protected]> Acked-by: Michael S. Tsirkin <[email protected]> Signed-off-by: David S. Miller <[email protected]>
tomthink · Jan 1, 2019 · aff6db4 · aff6db4
1 parent 4087d2b
commit aff6db4
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
@@ -573,6 +573,8 @@ static inline void **__ptr_ring_swap_queue(struct ptr_ring *r, void **queue,
 		else if (destroy)
 			destroy(ptr);
 
+	if (producer >= size)
+		producer = 0;
 	__ptr_ring_set_size(r, size);
 	r->producer = producer;
 	r->consumer_head = 0;