diff options
| author | Lin Ma <linma@zju.edu.cn> | 2021-11-15 22:56:00 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-11-26 10:47:20 +0100 |
| commit | e418bb556ff801e11592851fd465415757a2ef68 (patch) | |
| tree | 10158a28da173c1d321be31a9af2ac7897d8c12f /net/nfc | |
| parent | bbb8376d58ac25f7552646df579d550fbf8190ec (diff) | |
NFC: reorganize the functions in nci_request
[ 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>
Diffstat (limited to 'net/nfc')
| -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 6a34a0a786ea..1d0aa9e6044b 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; |