From: Lin Ma linma@zju.edu.cn
commit 48b71a9e66c2eab60564b1b1c85f4928ed04e406 upstream.
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 Link: https://lore.kernel.org/r/20211116152732.19238-1-linma@zju.edu.cn Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/nfc/nci_core.h | 1 + net/nfc/nci/core.c | 19 +++++++++++++++++-- 2 files changed, 18 insertions(+), 2 deletions(-)
--- a/include/net/nfc/nci_core.h +++ b/include/net/nfc/nci_core.h @@ -42,6 +42,7 @@ enum nci_flag { NCI_UP, NCI_DATA_EXCHANGE, NCI_DATA_EXCHANGE_TO, + NCI_UNREG, };
/* NCI device states */ --- a/net/nfc/nci/core.c +++ b/net/nfc/nci/core.c @@ -485,6 +485,11 @@ static int nci_open_device(struct nci_de
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; @@ -548,6 +553,10 @@ done: 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)) { @@ -585,8 +594,8 @@ static int nci_close_device(struct nci_d /* Flush cmd wq */ flush_workqueue(ndev->cmd_wq);
- /* Clear flags */ - ndev->flags = 0; + /* Clear flags except NCI_UNREG */ + ndev->flags &= BIT(NCI_UNREG);
mutex_unlock(&ndev->req_lock);
@@ -1268,6 +1277,12 @@ void nci_unregister_device(struct nci_de { 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);