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nfc: nci: clear NCI_DATA_EXCHANGE before calling completion callback

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Move clear_bit(NCI_DATA_EXCHANGE) before invoking the data exchange
callback in nci_data_exchange_complete().

The callback (e.g. rawsock_data_exchange_complete) may immediately
schedule another data exchange via schedule_work(tx_work).  On a
multi-CPU system, tx_work can run and reach nci_transceive() before
the current nci_data_exchange_complete() clears the flag, causing
test_and_set_bit(NCI_DATA_EXCHANGE) to return -EBUSY and the new
transfer to fail.

This causes intermittent flakes in nci/nci_dev in NIPA:

  # #  RUN           NCI.NCI1_0.t4t_tag_read ...
  # # t4t_tag_read: Test terminated by timeout
  # #          FAIL  NCI.NCI1_0.t4t_tag_read
  # not ok 3 NCI.NCI1_0.t4t_tag_read

Fixes: 38f04c6b1b ("NFC: protect nci_data_exchange transactions")
Reviewed-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20260303162346.2071888-5-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2026-03-03 08:23:44 -08:00
parent 6608358194
commit 0efdc02f4f
1 changed files with 8 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

12
net/nfc/nci/data.c
View file

@ -33,7 +33,8 @@ void nci_data_exchange_complete(struct nci_dev *ndev, struct sk_buff *skb,
conn_info = nci_get_conn_info_by_conn_id(ndev, conn_id);
if (!conn_info) {
kfree_skb(skb);
goto exit;
clear_bit(NCI_DATA_EXCHANGE, &ndev->flags);
return;
}
cb = conn_info->data_exchange_cb;
@ -45,6 +46,12 @@ void nci_data_exchange_complete(struct nci_dev *ndev, struct sk_buff *skb,
timer_delete_sync(&ndev->data_timer);
clear_bit(NCI_DATA_EXCHANGE_TO, &ndev->flags);
/* Mark the exchange as done before calling the callback.
* The callback (e.g. rawsock_data_exchange_complete) may
* want to immediately queue another data exchange.
*/
clear_bit(NCI_DATA_EXCHANGE, &ndev->flags);
if (cb) {
/* forward skb to nfc core */
cb(cb_context, skb, err);
@ -54,9 +61,6 @@ void nci_data_exchange_complete(struct nci_dev *ndev, struct sk_buff *skb,
/* no waiting callback, free skb */
kfree_skb(skb);
}
exit:
clear_bit(NCI_DATA_EXCHANGE, &ndev->flags);
}
/* ----------------- NCI TX Data ----------------- */