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authorLin Ma <linma@zju.edu.cn>2021-11-15 17:56:00 +0300
committerJakub Kicinski <kuba@kernel.org>2021-11-18 07:16:53 +0300
commit86cdf8e38792545161dbe3350a7eced558ba4d15 (patch)
tree993f3eb88e7320334cf6776cf8413263ddb049a3 /net/nfc/nci
parent3e6db079751afd527bf3db32314ae938dc571916 (diff)
downloadlinux-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.c11
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;