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NFC: reorganize the functions in nci_request

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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 e2cb6b891a ("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: 6a2968aaf5 ("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>
This commit is contained in:
Lin Ma 2021-11-15 22:56:00 +08:00 committed by Jakub Kicinski
parent 3e6db07975
commit 86cdf8e387
1 changed files with 7 additions and 4 deletions
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11
net/nfc/nci/core.c
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@ -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;