| Message ID | 20211115142938.8109-1-linma@zju.edu.cn (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v0] NFC: reorganize the functions in nci_request | expand |
11/15/21 5:29 PM, Lin Ma пишет: > 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(). Please add Fixes tag > > Signed-off-by: Lin Ma <linma@zju.edu.cn> > --- > 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 6fd873aa86be..2ab2d6a1a143 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; >
diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c index 6fd873aa86be..2ab2d6a1a143 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;
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> --- net/nfc/nci/core.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)