From: Lin Ma linma@zju.edu.cn
[ Upstream commit 3e3b5dfcd16a3e254aab61bd1e8c417dd4503102 ]
There is a potential UAF between the unregistration routine and the NFC netlink operations.
The race that cause that UAF can be shown as below:
(FREE) | (USE) nfcmrvl_nci_unregister_dev | nfc_genl_dev_up nci_close_device | nci_unregister_device | nfc_get_device nfc_unregister_device | nfc_dev_up rfkill_destory | device_del | rfkill_blocked ... | ...
The root cause for this race is concluded below: 1. The rfkill_blocked (USE) in nfc_dev_up is supposed to be placed after the device_is_registered check. 2. Since the netlink operations are possible just after the device_add in nfc_register_device, the nfc_dev_up() can happen anywhere during the rfkill creation process, which leads to data race.
This patch reorder these actions to permit 1. Once device_del is finished, the nfc_dev_up cannot dereference the rfkill object. 2. The rfkill_register need to be placed after the device_add of nfc_dev because the parent device need to be created first. So this patch keeps the order but inject device_lock to prevent the data race.
Signed-off-by: Lin Ma linma@zju.edu.cn Fixes: be055b2f89b5 ("NFC: RFKILL support") Reviewed-by: Jakub Kicinski kuba@kernel.org Reviewed-by: Krzysztof Kozlowski krzysztof.kozlowski@canonical.com Link: https://lore.kernel.org/r/20211116152652.19217-1-linma@zju.edu.cn Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/nfc/core.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-)
diff --git a/net/nfc/core.c b/net/nfc/core.c index 3c645c1d99c9b..dc7a2404efdf9 100644 --- a/net/nfc/core.c +++ b/net/nfc/core.c @@ -94,13 +94,13 @@ int nfc_dev_up(struct nfc_dev *dev)
device_lock(&dev->dev);
- if (dev->rfkill && rfkill_blocked(dev->rfkill)) { - rc = -ERFKILL; + if (!device_is_registered(&dev->dev)) { + rc = -ENODEV; goto error; }
- if (!device_is_registered(&dev->dev)) { - rc = -ENODEV; + if (dev->rfkill && rfkill_blocked(dev->rfkill)) { + rc = -ERFKILL; goto error; }
@@ -1125,11 +1125,7 @@ int nfc_register_device(struct nfc_dev *dev) if (rc) pr_err("Could not register llcp device\n");
- rc = nfc_genl_device_added(dev); - if (rc) - pr_debug("The userspace won't be notified that the device %s was added\n", - dev_name(&dev->dev)); - + device_lock(&dev->dev); dev->rfkill = rfkill_alloc(dev_name(&dev->dev), &dev->dev, RFKILL_TYPE_NFC, &nfc_rfkill_ops, dev); if (dev->rfkill) { @@ -1138,6 +1134,12 @@ int nfc_register_device(struct nfc_dev *dev) dev->rfkill = NULL; } } + device_unlock(&dev->dev); + + rc = nfc_genl_device_added(dev); + if (rc) + pr_debug("The userspace won't be notified that the device %s was added\n", + dev_name(&dev->dev));
return 0; } @@ -1154,10 +1156,17 @@ void nfc_unregister_device(struct nfc_dev *dev)
pr_debug("dev_name=%s\n", dev_name(&dev->dev));
+ rc = nfc_genl_device_removed(dev); + if (rc) + pr_debug("The userspace won't be notified that the device %s " + "was removed\n", dev_name(&dev->dev)); + + device_lock(&dev->dev); if (dev->rfkill) { rfkill_unregister(dev->rfkill); rfkill_destroy(dev->rfkill); } + device_unlock(&dev->dev);
if (dev->ops->check_presence) { device_lock(&dev->dev); @@ -1167,11 +1176,6 @@ void nfc_unregister_device(struct nfc_dev *dev) cancel_work_sync(&dev->check_pres_work); }
- rc = nfc_genl_device_removed(dev); - if (rc) - pr_debug("The userspace won't be notified that the device %s " - "was removed\n", dev_name(&dev->dev)); - nfc_llcp_unregister_device(dev);
mutex_lock(&nfc_devlist_mutex);