From: Lin Ma linma@zju.edu.cn
[ Upstream commit 86cdf8e38792545161dbe3350a7eced558ba4d15 ]
There is a possible data race as shown below:
thread-A in nci_request() | thread-B in nci_close_device() | mutex_lock(&ndev->req_lock); test_bit(NCI_UP, &ndev->flags); | ... | test_and_clear_bit(NCI_UP, &ndev->flags) mutex_lock(&ndev->req_lock); | |
This race will allow __nci_request() to be awaked while the device is getting removed.
Similar to commit e2cb6b891ad2 ("bluetooth: eliminate the potential race condition when removing the HCI controller"). this patch alters the function sequence in nci_request() to prevent the data races between the nci_close_device().
Signed-off-by: Lin Ma linma@zju.edu.cn Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation") Link: https://lore.kernel.org/r/20211115145600.8320-1-linma@zju.edu.cn Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/nfc/nci/core.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c index 32e8154363cab..5e55cb6c087a2 100644 --- a/net/nfc/nci/core.c +++ b/net/nfc/nci/core.c @@ -144,12 +144,15 @@ inline int nci_request(struct nci_dev *ndev, { int rc;
- if (!test_bit(NCI_UP, &ndev->flags)) - return -ENETDOWN; - /* Serialize all requests */ mutex_lock(&ndev->req_lock); - rc = __nci_request(ndev, req, opt, timeout); + /* check the state after obtaing the lock against any races + * from nci_close_device when the device gets removed. + */ + if (test_bit(NCI_UP, &ndev->flags)) + rc = __nci_request(ndev, req, opt, timeout); + else + rc = -ENETDOWN; mutex_unlock(&ndev->req_lock);
return rc;