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authorLin Ma <linma@zju.edu.cn>2021-11-16 18:27:32 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-12-01 11:27:43 +0300
commit2350cffd71e74bf81dedc989fdec12aebe89a4a5 (patch)
treee85317c1cf20085a2fd149fc6b107e25cd2bdfee /net
parentb0313bc7f5fbb6beee327af39d818ffdc921821a (diff)
downloadlinux-2350cffd71e74bf81dedc989fdec12aebe89a4a5.tar.xz
NFC: add NCI_UNREG flag to eliminate the race
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>
Diffstat (limited to 'net')
-rw-r--r--net/nfc/nci/core.c19
1 files changed, 17 insertions, 2 deletions
diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index 1008bbbb3af9..0e0dff72a9e4 100644
--- a/net/nfc/nci/core.c
+++ b/net/nfc/nci/core.c
@@ -485,6 +485,11 @@ 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;
@@ -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_dev *ndev)
/* 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_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);