[PATCH 4.14 10/77] nfc/nci: fix race with opening and closing

Greg Kroah-Hartman
2022-12-05T19:16:20Z

From: Lin Ma <linma@zju.edu.cn>

[ Upstream commit 0ad6bded175e829c2ca261529c9dce39a32a042d ]

Previously we leverage NCI_UNREG and the lock inside nci_close_device to
prevent the race condition between opening a device and closing a
device. However, it still has problem because a failed opening command
will erase the NCI_UNREG flag and allow another opening command to
bypass the status checking.

This fix corrects that by making sure the NCI_UNREG is held.

Reported-by: syzbot+43475bf3cfbd6e41f5b7@syzkaller.appspotmail.com
Fixes: 48b71a9e66c2 ("NFC: add NCI_UNREG flag to eliminate the race")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/nfc/nci/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index 99f4573fd917..216228c39acb 100644
--- a/net/nfc/nci/core.c
+++ b/net/nfc/nci/core.c
@@ -542,7 +542,7 @@ static int nci_open_device(struct nci_dev *ndev)
skb_queue_purge(&ndev->tx_q);

ndev->ops->close(ndev);
- ndev->flags = 0;
+ ndev->flags &= BIT(NCI_UNREG);
}

done:
--
2.35.1