@@ -30,6 +30,7 @@ enum nci_flag {
NCI_UP,
NCI_DATA_EXCHANGE,
NCI_DATA_EXCHANGE_TO,
+ NCI_UNREG,
};
/* NCI device states */
@@ -473,6 +473,11 @@ static int nci_open_device(struct nci_dev *ndev)
mutex_lock(&ndev->req_lock);
+ if (test_bit(NCI_UNREG, &ndev->flags)) {
+ rc = -ENODEV;
+ goto done;
+ }
+
if (test_bit(NCI_UP, &ndev->flags)) {
rc = -EALREADY;
goto done;
@@ -545,6 +550,10 @@ static int nci_open_device(struct nci_dev *ndev)
static int nci_close_device(struct nci_dev *ndev)
{
nci_req_cancel(ndev, ENODEV);
+
+ /* This mutex needs to be held as a barrier for
+ * caller nci_unregister_device
+ */
mutex_lock(&ndev->req_lock);
if (!test_and_clear_bit(NCI_UP, &ndev->flags)) {
@@ -582,8 +591,8 @@ static int nci_close_device(struct nci_dev *ndev)
del_timer_sync(&ndev->cmd_timer);
- /* Clear flags */
- ndev->flags = 0;
+ /* Clear flags except NCI_UNREG */
+ ndev->flags &= BIT(NCI_UNREG);
mutex_unlock(&ndev->req_lock);
@@ -1266,6 +1275,12 @@ void nci_unregister_device(struct nci_dev *ndev)
{
struct nci_conn_info *conn_info, *n;
+ /* This set_bit is not protected with specialized barrier,
+ * However, it is fine because the mutex_lock(&ndev->req_lock);
+ * in nci_close_device() will help to emit one.
+ */
+ set_bit(NCI_UNREG, &ndev->flags);
+
nci_close_device(ndev);
destroy_workqueue(ndev->cmd_wq);
There are two sites that calls queue_work() after the destroy_workqueue() and lead to possible UAF. The first site is nci_send_cmd(), which can happen after the nci_close_device as below nfcmrvl_nci_unregister_dev | nfc_genl_dev_up nci_close_device | flush_workqueue | del_timer_sync | nci_unregister_device | nfc_get_device destroy_workqueue | nfc_dev_up nfc_unregister_device | nci_dev_up device_del | nci_open_device | __nci_request | nci_send_cmd | queue_work !!! Another site is nci_cmd_timer, awaked by the nci_cmd_work from the nci_send_cmd. ... | ... nci_unregister_device | queue_work destroy_workqueue | nfc_unregister_device | ... device_del | nci_cmd_work | mod_timer | ... | nci_cmd_timer | queue_work !!! For the above two UAF, the root cause is that the nfc_dev_up can race between the nci_unregister_device routine. Therefore, this patch introduce NCI_UNREG flag to easily eliminate the possible race. In addition, the mutex_lock in nci_close_device can act as a barrier. Signed-off-by: Lin Ma <linma@zju.edu.cn> Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation") Reviewed-by: Jakub Kicinski <kuba@kernel.org> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> --- include/net/nfc/nci_core.h | 1 + net/nfc/nci/core.c | 19 +++++++++++++++++-- 2 files changed, 18 insertions(+), 2 deletions(-)