xsk: fix poll/POLLIN premature returns

Polling for the ingress queues relies on reading the producer/consumer
pointers of the Rx queue.

Prior this commit, a cached consumer pointer could be used, instead of
the actual consumer pointer and therefore report POLLIN prematurely.

This patch makes sure that the non-cached consumer pointer is used
instead.

Reported-by: Qi Zhang <qi.z.zhang@intel.com>
Tested-by: Qi Zhang <qi.z.zhang@intel.com>
Fixes: c497176cb2e4 ("xsk: add Rx receive functions and poll support")
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index 52ecaf770642785140358ea4ff2713ccaca8a489..8a64b150be546d2d5903bbc62e1b32525e73d992 100644 (file)
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -250,7 +250,7 @@ static inline bool xskq_full_desc(struct xsk_queue *q)
 
 static inline bool xskq_empty_desc(struct xsk_queue *q)
 {
-       return xskq_nb_free(q, q->prod_tail, 1) == q->nentries;
+       return xskq_nb_free(q, q->prod_tail, q->nentries) == q->nentries;
 }
 
 void xskq_set_umem(struct xsk_queue *q, struct xdp_umem_props *umem_props);