__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: 5d49de532002 ("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]> --- 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 6894976b54e3..186cd8e970c7 100644 --- 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; -- 2.19.2
