diff options
| author | Lin Ma <linma@zju.edu.cn> | 2021-11-15 17:56:00 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2021-11-18 07:16:53 +0300 |
| commit | 86cdf8e38792545161dbe3350a7eced558ba4d15 (patch) | |
| tree | 993f3eb88e7320334cf6776cf8413263ddb049a3 /net/nfc/nci | |
| parent | 3e6db079751afd527bf3db32314ae938dc571916 (diff) | |
| download | linux-86cdf8e38792545161dbe3350a7eced558ba4d15.tar.xz | |
NFC: reorganize the functions in nci_request
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>
Diffstat (limited to 'net/nfc/nci')
| -rw-r--r-- | net/nfc/nci/core.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c index 6fd873aa86be..1dd0269c1a72 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; |