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Commit 20b52a75 authored by Magnus Karlsson's avatar Magnus Karlsson Committed by Alexei Starovoitov
Browse files

xsk: fix potential lost completion message in SKB path 



The code in xskq_produce_addr erroneously checked if there
was up to LAZY_UPDATE_THRESHOLD amount of space in the completion
queue. It only needs to check if there is one slot left in the
queue. This bug could under some circumstances lead to a WARN_ON_ONCE
being triggered and the completion message to user space being lost.

Fixes: 35fcde7f ("xsk: support for Tx")
Signed-off-by: default avatarMagnus Karlsson <magnus.karlsson@intel.com>
Reported-by: default avatarPavel Odintsov <pavel@fastnetmon.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent d0fbad0a

net/xdp/xsk_queue.h

+2 −7
Original line number Diff line number Diff line
@@ -62,14 +62,9 @@ static inline u32 xskq_nb_avail(struct xsk_queue *q, u32 dcnt) 
	return (entries > dcnt) ? dcnt : entries;

}



static inline u32 xskq_nb_free_lazy(struct xsk_queue *q, u32 producer)

{

	return q->nentries - (producer - q->cons_tail);

}



static inline u32 xskq_nb_free(struct xsk_queue *q, u32 producer, u32 dcnt)

{

	u32 free_entries = xskq_nb_free_lazy(q, producer);

	u32 free_entries = q->nentries - (producer - q->cons_tail);



	if (free_entries >= dcnt)

		return free_entries;
@@ -129,7 +124,7 @@ static inline int xskq_produce_addr(struct xsk_queue *q, u64 addr) 
{

	struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;



	if (xskq_nb_free(q, q->prod_tail, LAZY_UPDATE_THRESHOLD) == 0)

	if (xskq_nb_free(q, q->prod_tail, 1) == 0)

		return -ENOSPC;



	ring->desc[q->prod_tail++ & q->ring_mask] = addr;